She was originally created under the name "Megan" but changed to Rosa when Stephanie Beatriz got the part over Chelsea Peretti, who would go on to portray Gina Linetti.

Rosa's character is serious, confident, and frequently angry; she is closed-off and does not share details about her personal life, although the audience gets glimpses into her past at various points.

[3]Beatriz was eventually given the role,[3] causing Brooklyn Nine-Nine creators Michael Schur and Dan Goor to change the name of the character to Rosa Diaz in search of a name less intense and more "flowery".

"[6] Melissa Fumero told Parents that because of her and Beatriz's fear of being fired, they privately agreed to distance their characters' styles from each other, with Amy adopting straight hair while Rosa made hers more curly.

[6][10] Details of Rosa's life are mentioned at times; she is, at various points, known to have obtained a pilot's license, gone to medical school, rented an apartment under a fake name, gone through the juvenile detention system,[10] and been expelled from dance academy for assaulting ballerinas.

[10] Writing for Comic Book Resources, Ian Goodwillie estimates that Rosa was approaching the age of 40 by the end of the show's eight-season run.

Goodwillie casts doubt on the veracity of some of the details of her backstory, noting that Rosa's willingness to lie about her name in renting an apartment shakes confidence in the notion that she had lived such an eventful past life.

Beatriz later remarked that she was "thrilled by it",[6] and that she wanted Rosa to serve as a positive example for teenagers and young adults as a bisexual character, a category she thought severely lacked representation.

[13] Palmer Haasch with Polygon reported a statement from Dan Goor, claiming that Rosa's declaration, "I'm bi", was the first time the phrase had been used on network television.

Haash, however, contradicted the claim: At least two prior shows, Grey's Anatomy and Crazy Ex-Girlfriend, had used the phrase as well, although she argued that Goor's statement still drew necessary attention to the rarity of bisexual representation onscreen.

[11] According to The Washington Post, queer fans of color were quick to note that Fox's cancellation of Brooklyn Nine-Nine came one day after Rosa came out on the show.

Maggie Lange, writing for GQ, praised Rosa for her ability to capture scenes among more outstanding personalities such as Jake Peralta and Gina Linetti.

[13] Polygon noted that fans at Brooklyn Nine-Nine's San Diego Comic-Con panel that year repeatedly thanked Stephanie Beatriz for her portrayal.