Roquefort is a small mouse who resides in a mousehole located in Madame Bonfamille's mansion. He is good friends with Duchess, a female cat, and her three kittens, Toulouse, Berlioz, and Marie; he also seems to have a friendly relationship with Frou-Frou. His devotion to the Aristocats is shown when he goes out searching for them when the family goes missing.
Despite being on friendly terms with Duchess and her kittens, he seems to be naturally afraid of other cats, though he places this fear aside to assist his friends.
Roquefort is introduced as Duchess and her kittens are preparing to eat the special dinner Edgar has prepared for them. Roquefort is invited to dinner by the kittens and produces a cracker he had brought with him, dipping it into the milk. Unknown to any of them, Edgar laced the milk with sleeping pills, and Roquefort is knocked unconscious as he tries to return to his mouse hole for another cracker.
After Duchess and her kittens are catnapped, he spends all night searching the streets of Paris for them but is unsuccessful. He reports to Frou-Frou to tell her the sad news. Edgar suddenly walks in the stable with an unusually cheerful grin, and Roquefort deduces that Edgar was responsible for kidnapping Duchess and her kittens after overhearing him gloating over his making the headlines (specifically, referring to his using the bike to abandon the cats into the wild).
Later, Roquefort tries to hitch a ride on Edgar's motorcycle, but gets bumped up and down several times and coughs up smoke that was blown at him, then was flung off of the motorcycle and into the street.
Later, when the cats return, he notices Edgar, but before Roquefort could warn Duchess and her kittens, the butler catches them in a sack and locks them in an unused oven with plans to mail the cats to Timbuktu. At Duchess's request, Roquefort manages to find O'Malley, the alley cat who had guided the family back to Paris. However, because the oven grate was closed and thus blocked out their words, Roquefort misheard and thought they called him some other name.
Upon meeting O'Malley, Roquefort informs him of the situation. O'Malley immediately heads toward the mansion. He tasks Roquefort with rounding up Scat Cat's gang of Alley Cats. Roquefort reminds O'Malley that he is a mouse, but O'Malley tells Roquefort that the cats will not harm him if Roquefort gives O'Malley's name.
Roquefort meets up with Scat Cat and the alley cats and tries to get them to help, but is unable to remember O'Malley's name and is forced to take cover inside a bottle. The alley cats prepare to eat him, but Roquefort yells out the proper name in frustration when asked for last words. The alley cats head off to help O'Malley, leaving Roquefort to chase them down in an attempt to lead them to the correct house. Coincidentally, this also led to a Frenchman to consider giving up drinking wine after he witnessed a mouse (Roquefort) seemingly chasing the cats. Believing he was hallucinating, the Frenchman poured his wine onto the ground.
During the resultant fight between the alley cats and Edgar, Roquefort attempts to release Duchess's family by cracking the combination lock, abruptly yelling for silence in order to hear better. After Edgar is defeated, Roquefort presumably remains in Madame Bonfamille's home with the cats. He is last seen conducting Scat Cat and his band to the song, "Everybody Wants to Be a Cat".
- Roquefort's name seems to come from a particular kind of sheep's milk cheese that is made in the southern portion of France.
- Wally Cox, Red Buttons and John Fiedler were all considered to voice Roquefort before Sterling Holloway was chosen.
- Roquefort's coughing noises were recycled sounds from Archimedes in The Sword in the Stone.
- In the storybook LP record soundtrack of the movie, Roquefort mentions his hero is Sherlock Holmes, hence his detective clothes.