Rosa is one of Papi and Chloe's daughters along with Lala, Ali, Pep, and her brother Papi Jr., which their parents try to keep up with. Her father, Papi, tells Rosa and her siblings some incredible tales about the heroic Chihuahua. However, her father embellishes his stories to the point in which Rosa and her siblings end up causing mayhem. Later on, Rosa's mother, Chloe, along with Papi, Delgado and Pedro (Papi's adoptive brother), participate in a dog fashion show so they can win a large cash prize that would save Sam and Rachel's family home. Eager to help out, Rosa and her siblings venture out and find some bank robbers who had stolen a large sum of money. Rosa and her siblings stow away in one of the bags, but are later found out by the robbers. Papi and Chloe, along with Pedro and Delgado, come to the puppies' aid and are able to defeat the bank robbers. Papi scolds Rosa and the kids for running off, but Chloe tells Papi that they did manage to capture the robbers and were trying to save their home, so Papi lets them off lightly. Thanks to the puppies, they were awarded more than enough money to save their house and live happily ever after.
In Beverly Hills Chihuahua 3, Rosa is considered "the runt of the litter" by her siblings and everyone else. She is almost fifteen in dog years and wants a quinceañera.