Originally, Zoro was planned by Oda to be the bodyguard of Buggy. A picture of an incarnation of him in Buggy's crew was then later released in Volume 3 along with another picture of Buggy's crew. Oda described Buggy's crew as a family unit, in which Zoro was the elder brother.
Zoro has occasionally appeared wearing glasses in some of the color illustrations by Oda and in the 11th opening of the anime.
His adventure in Shikkearu Kingdom is also extended in the anime.
Not only did Perona refuse to give Zoro his swords back, but she also tried to turn Zoro into her servant by using her Devil Fruit powers. She got as far as managing to dress Zoro like her former subordinate, Kumashi (covered in bandages), while he had passed out before he woke up and left the room in search of his swords. In the anime, Zoro's training will begin by defeating the leader of the humandrills who copied the swordsmanship of Mihawk.
In most fillers, his lack of direction is further ridiculed as he has gone in the wrong direction even though his guide was still pointing in the correct way, and even turning to the right on a straight path.
Also, ever since episode 111, Zoro has been called marimo (moss-head in the dub) by Sanji in reference to his oddly colored green hair.
Zoro makes a cameo appearance in the anime, Sayonara Zetsubou Sensei: during Meru's introduction, Harumi is seen reading a yaoi manga featuring Sanji and Zoro. Also, in her room, we can see action figures of Luffy, Zoro, Sanji and Sogeking.
In an episode of Kuroko no Basuke, an old man that is mopping the floor of the bathroom was dressed like Zoro.
In The Simpsons episode "Treehouse of Horror XXV", several other incarnations from other animated franchises of the family are shown, each one with a respective theme. In the anime theme, each of the family members was depicted as a specific anime character, Homer is seen as Zoro, complete with green hair, three katana, and Zoro's post-timeskip outfit.
In an episode of Sayonara Zetsubou Sensei, in Harumi's room, we can see action figures of Luffy, Zoro, Sanji, and Sogeking.
In the episode 7 from Nurarihyon no Mago Sennen Makyo, the character Itaku use two sickles in his hands and the third in his mouth as Zoro
Zoro appeared in the 13th episode of the third season of the popular YouTube series, "DEATH BATTLE!", where he fought Erza Scarlet from the Fairy Tail franchise and won. Before that, he fought Kenshin Himura from the Rurouni Kenshin series in the second season of the spin-off series, "One Minute Melee" and won. Later on, he appeared in Death Battle's other spin-off series, DBX, where he once again fought Rurouni Kenshin and won.
Zoro's past was expanded upon in the anime. Zoro was a traveler who went around defeating dojos for their signs. However, there was one person Zoro could not beat - the sensei's daughter, Kuina. In the anime she is the reason he joins her father's dojo in the first place. Kuina's father made a deal that if he could defeat her Zoro would take the sign. If not, Zoro would have to train under him. When given the opportunity to use as many swords as he wanted, he grabbed as many as he could carry and faced off against Kuina. He lost and was told he had to start with one sword before he could use more. As per the consequences of his loss, he trained at the dojo as promised.
In the manga, Zoro enters to see her dead body, eyes covered and surrounded by the students and accuses her of running away, in the anime no such scene is shown, but a funeral takes place for her instead, though later on "Ocean Dream" arc in the anime, the original manga scene is shown in a flashback.
His story is extended also in the anime by showing the time he first met and befriended Johnny and Yosaku. They cash in when Zoro takes out a large bounty and, given they pay his tab at the bar he was at for his food, can keep the rest of the money for themselves as an apology for taking their 'head'. Later, Dick appears in the town with his horde of bandits, who proceed to loot the town. Johnny and Yosaku watch as a child tries to stop the thief to no avail. Johnny convinces Yosaku that they must stop him, to which Yosaku reluctantly agrees. The two are no match for Dick, but luckily Zoro comes to claim the bounty on Dick's head to pay for a katana that he broke. After a complete victory by Zoro, Johnny and Yosaku look up to Zoro and start to call him "Aniki".
Most of Zoro's attacks are puns and some also have religious connections. One of Zoro's more common attacks, Oni Giri (Demon Slash), is a pun on the Japanese word onigiri (rice ball). Another common attack, the 36/72/108 Pondo Hou, is a reference to the 36 passions of Buddhism. Another one of Zoro's powers, Asura, also borrows from a religion by taking its name from a group of Hindu demons. This is a bit ironic considering that Zoro is a stated apatheist, and Nami and Chopper have both claimed that Zoro is more arrogant than the self-proclaimed "god" Enel.
In the 4Kids English dub of One Piece, Zoro is referred to as "Zolo", however when FUNimation picked up the series, they reverted his name back to "Zoro", only keeping "Zolo" for the broadcast Skypiea episodes for consistency. Originally, the English version of the manga by VIZ spelled his name as "Roronoa Zoro", but it was changed to "Zolo" in chapter 50. It is possible that this name change was either a result of trademark issues with Zorro - who shares a similar name - or to maintain similarities to the 4Kids dub. In the book The Anime Encyclopedia - A guide to Japanese animation since 1917 (2001), Zoro's name was spelled "Zorro" in the One Piece entry. Such cases as this have been common in many translations across the world, mostly because of the similarity between the two names. To date, however, this has yet to raise concerns over copyright between the two characters. However, in the second 2011 volume of the U.S. Shonen Jump magazine, Zoro's name was changed back to "Zoro". This is the first time Viz has called the character this since its first printings of Chapter 50. It was changed back to "Zolo" in the following issues, however.
In Japanese promotions and in some art work, the character is often referred to as "Zoro" but is also spelled "Zolo" in a few cases, mostly in promotions.  However, there are fans that claim that "Zoro" was the creator's intended spelling, since it is almost always spelled that way in art and it is supposed to be based off the aforementioned character "Zorro". However, the appearance of "Zolo" in Japan can be explained without relating it to 4Kids or copyright laws due to interchangeable L and R sounds. Other characters who have displayed this problem include Franky (Flanky) and Robin (Lobin). In the end, in noted cases English speaking fans may choose to specifically refer to the dub version of Zoro as "Zolo", while referring to the original version as "Zoro".
In the English dub by 4Kids, Kuina's death was removed. Instead, she was rewritten to have been seriously injured by a group from a nearby town, leaving her unable to fight; a situation which, ironically, is more violent than the original. Zoro's commitment, therefore, is to continue fighting for her sake, instead of in honor of her death. During the Drum Island Arc in the 4Kids dub, when the ankle scars he obtained during his fight with Mr. 3 were exposed, they were rewritten to have been gained from a bear trap since the Straw Hats never visited Little Garden in that version.
Zoro with Luffy's scar in the Shonen Jump print of Chapter 698
Zoro with the correct scar in the Volume 70.
Zoro has quite a few art errors during the serialization in the chapters. They have been corrected in their respective volumes.
In Jump's edition of Chapter 598, he was shown to have a scar on his right eye, but in the next chapter, it is moved to his left eye. Oda wrote in 599 that the right eye scar was an error, and that the one with the scar on the left eye is the correct one. The error was corrected in volume 61.
In the last panel of page 16 of Chapter 698, Zoro is seen with the wrong scar on his chest. Instead of the thin diagonal line given by Mihawk, he had the thick cross Luffy got from Akainu. This was corrected in volume 70.
On the cover art of Chapter 699, Zoro is seen missing the scar on his left eye. This was corrected in volume 70.
In the anime, Zoro's wanted poster did not include Usopp's shadow the first time that the bounty was issued, but this was later corrected in Episode 152. When the second bounty was issued Usopp's shadow was inexplicably omitted again.
On the cover of Chapter 77, a chicken is seen holding a newspaper that says "Wanted, Roronoa Zoro, 1,000,000". This bounty is not canon however, because the covers do not relate to the main series (unless it is a cover story).
In Chapter 599, Zoro's Shusui was shown with a different saya strongly resembling that of Trafalgar Law's nodachi. Although Oda did not write anything about it, it could be taken as a mistake as Zoro is then seen holding Shusui with its traditional sheath with no comments about the change. This error is fixed in the anime chapter that adapts this scene from the manga.
Zoro has his own jolly roger, like all the Straw Hat crew. It has Zoro's bandanna, two swords instead of crossbones, and a sword in its mouth (the white hilt suggests that it is Wado Ichimonji, which is always the one that Zoro holds in his mouth when using Santoryu).
After the timeskip, the skull gains Zoro's three earrings and the left eye is closed with a vertical scar over it to match Zoro's own eye. The swords that make up the crossbones are more detailed: the blade pointing towards the right is dark, suggesting that it is Shusui while the other is Sandai Kitetsu.
Another jolly roger is seen on his armor in the cover of Chapter 699. This jolly roger is a regular skull with three swords crossing behind it.
Zoro is the only member of the crew that Luffy personally sought out to invite before they actually met.
Zoro is the only Straw Hat Pirate to be named after a real life pirate, this being after the Japanese pronunciation of François l'Ollonais.
Zoro is the first known person since Ryuma to kill a dragon, an act which made the latter a legend. Both of them also killed the dragon the same way, by decapitation in the air.
Along with Killer, Zoro is only one of two members of the Worst Generation who do not have a Devil Fruit power. Incidentally, they are the only two who are subordinates rather than a captain.
Zoro's reintroduction to the series after the timeskip is reminiscent of how Mihawk was introduced. Both sliced a galleon in two and both seemingly did so due to an interrupted nap.
Zoro has had the most English dub voice actors out of all the Straw Hats (2 as an adult, 4 as a child).
In Japanese fan polls, Zoro was consistently the second most popular character, until his position was usurped by Law in the fifth poll, but he reclaimed it in the sixth poll. Furthermore, in the attack popularity polls his Santoryu Ogi: Sanzen Sekai came in 2nd.
Zoro is the highest bounty starter on the East Blue with 60,000,000 bounty, defeating Luffy that amounts double of his initial bounty ( 30,000,000).
Oda has hinted that one of the reasons why Zoro uses sushi-based puns in his Nigiri attacks is because he has never tried sushi and has some sort of fascination with it. However, this can be considered one of Oda's SBS jokes.
Zoro's favorite foods are white rice, sea monster meat, and anything that goes with sake. His least favorite food is chocolate because it is too sweet.
Zoro also does not like ice cream, the same as Nami, Sanji and Franky.
Other than taking naps, Zoro typically sleeps at 4:00 A.M. and gets up at 7:00 A.M.
If the Straw Hat Pirates were not pirates, then Zoro would be a police officer.
Zoro's hobbies are training and drinking alcohol.
If the Straw Hat Pirates had a 50-meter race, then Zoro would come in fifth place. Oda clarifies that Zoro would be ranked higher in a shorter distance race, but Zoro would get lost in a longer race.