Rosie has a mother-like nature. She is mostly like a mother to the rhinoceros beetle, Dim, with whom she shares an act, and also the younger ants of the colony. She has apparently had twelve husbands who all died, making her (as she says) a "black widow widow." She sees her circus friends as her only true family.
Rosie is a black widow spider who has a mother-like nature. She is mostly like a mother to the rhinoceros beetle, Dim, with whom she shares an act, and also the younger ants of the colony.
Rosie works at P.T. Flea's circus as a rhinoceros tamer with her partner being the rhinoceros beetle Dim. During their opening act, Rosie cracks a whip at Dim as he roars ferociously. However, Rosie unintentionally lashes one of Dim's feet, causing him to cry in pain. Rosie consoles Dim and later attempts to put a Band-Aid over his "owie." Later on, Rosie and her circus troupe friends get fired after they accidentally burn P.T.
At the Bug Bar, they get into a fight with some flies, and Flik thought they were warriors and they thought that Flik was a manager searching for entertainment. She, along with her friends, then fly to Ant Island.
She is the one that tells Flik that they are circus artists and not warriors. After that, they attempt to leave the island, but are stopped by the attack of a bird. Rosie participates in the rescue of Dot and Francis by making a web to transport Flik, Dot, Francis, Tuck and Roll to safety. It is interesting to note that Rosie is very strong, as she carried the spider web with Flik, Dot, Francis, Tuck and Roll inside, and when it was cut accidentally by Francis, Rosie held them long enough to land on a tree.
After the rescue, the circus bugs agree to stay and support Flik's idea of making an artificial bird to scare Hopper and the grasshoppers away. Rosie participates in the making of the bird and then, at a party, she talks with an ant about her twelve deceased husbands, making her (as she says) a "black widow widow." When P.T. Flea arrives looking for the troupe and the flaming death act is a success, Rosie tries to tell him to keep quiet, but he ignores her, blowing Flik's cover in the process and they and Flik are banished by Atta. At the climax of the film, she participates in the final battle against the grasshoppers with Hopper being killed by the real bird after he mistook her for a fake and putting his reign of terror and insult on the ant colony to an end. She and her friends then leave the island with the promise of returning next spring.
- She is the first Pixar character to be voiced by Bonnie Hunt.
- During the outtakes, Rosie tries to say her line of telling Flik that they are not fighting grasshoppers, but is interrupted by someone hammering off screen, so she tells them to stop.
- During the same blooper reel where Tuck and Roll were supposed to be imitating the phrase: "You're fired!" and Rosie consequently yelling at them to shut up in irritation, Tuck and Roll enter a belching contest, with one of them proceeding to fart instead of burping, with Rosie saying, "I'm outta here," in a disgusted tone.