Roberta is a maid who worked for four years at the Lovelace household in Venezuela. Although her domestic skills, such as cleaning and cooking, were poor, she has developed a close friendship with the young scion of the Lovelace family, Garcia. Roberta was once known as Rosarita Cisneros, a former FARC guerrilla trained as an assassin in Cuba and an internationally wanted criminal. She earned the moniker "Bloodhound of Florencia" for her relentless drive to achieve her objectives.

In combat, Roberta is a truly fearsome opponent, having trained in a wide variety of martial, stealth, and weapon skills. Among the weapons she has used before were a sniper rifle, a combat knife, a shotgun disguised as an umbrella, a machine gun which was disguised as a briefcase, a grenade launcher, spiked brass knuckles, a trench spike, and pistols. Her strength, speed, endurance, and instincts were honed to almost supernatural levels.

There was even a scene in anime where she chased a car barefoot and used a knife to attach herself to it, that bore a striking resemblance to a similar scene from a movie Terminator 2 - the fact which Rock also indirectly points out and gets reprimanded by Dutch not to joke around.

It is ironic that while Roberta is one of the most powerful warrior-women in the story of Black Lagoon, she is also humane, possessing warmth, kindness, remorse, and family love for her master and his son.

She admitted that she did murder children, woman or anyone in name of revolution during her FARC years. Disillusioned by the fact that she is merely a tool for drug cartels in cahoots with FARC in the end, she opted out and joined the Lovelace clan as a maid. Despite being asked by Garcia not to pick up gunfighting anymore, later events of manga story make her go into battle again, seeking revenge.

She is also heavily modeled on El Mariachi, popularized by Antonio Banderas down to suitcase machine gun signature and her Latin America background.