Rosita worked as a bartender at Shorty's and collaborated with Doc and Jeremy to help create a serum for Dolls. At some point, Rosita and Doc develop a sexual relationship and continue the relationship even though Doc might have gotten Wynonna Earp pregnant. Doc encourages Rosita to bond with the Earp sisters, so she decides to throw a baby shower with Waverly Earp for Wynonna.
Waverly learned that Rosita is actually a Revenant (Doc knows) and promised to keep Rosie's secret from Wynonna. However Waverly spills the beans, leading Wynonna to threaten Rosita with Peacemaker, telling her that if she tests a serum to cure Nicole, Wynonna will "shoot her last". As she was planning to steal and sell Wynonna and Doc's baby for safe passage out of Purgatory, her relationship with Doc is dissolved.
Rosita has a PhD in Biochemistry and Engineering as well as an online certification in Astrology.