She is voiced by Michie Tomizawa in the Japanese version of the anime and Tabitha St. Germain in the English version.
Rosarita Cisneros is 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. (Balalaika refers her at one point as a "hardcore terrorist". Her tormented past and the smell of blood, gunpowder and muck like that of a sewer rat emanating from her was something Revy commented during their battle that she understood fully well.)
She admitted that she did murder children, women, or anyone in name of revolution during her FARC years. Eventually disillusioned by the realisation that she was merely a tool for the drug cartels in cahoots with FARC, she opted out and joined the Lovelace clan as a maid through her father who is a friend of Lovelace. Despite being asked by Garcia not to pick up gunfighting anymore, later events in the manga, which depicts her watching helplessly as a bomb was set killing many including Diego Lovelace. Garcia's question of why was his father was a victim makes her go into battle again, seeking revenge. Roberta also shows signs of a growing madness; she is shown taking mouthfuls of anti-psychotics, and experiencing haunting hallucinations in the form of her past victims, most notably a Japanese man. It is revealed that she tore his family picture before ruthlessly shooting him in the forehead. She once again stalks the city of Roanapur in search of the one responsible for assassinating her master. Unfortunately, it turns out to be the US Special Forces, who's intentions were to assassinate a general and had to sacrifice Diego Lovelace to complete their mission. Roberta's quest for vengeance has put many of the residents including Hotel Moscow, the Triad, and the Colombian Cartel on high alert as it could mean the end for all of them if their new enemy is the United States. Most of the residents blame the Lagoon Company for attracting her back to Roanapur despite the fact the group was in the dark about the situation and brushed it off as if it were an Elvis sighting. Further into her quest, she begins to lose sight of her goal, almost returning to her former persona to the point she begins to lose her sanity and has trouble identifying friend and foe, thus almost harming Garcia and Fabiola in the process. The Columbia Cartel even comments that she is no longer the hound they once knew, but a stray wolf searching for purpose. Her oath as the "Bloodhound of Florencia" is "In the name of Santa Maria, a hammer blow of righteousness to all injustice."
In Chapter 73, Roberta is last seen with an American woman, presumably Eda. The woman is able to disarm Roberta easily and pass her through the security, so whether she is Eda or not, she is definitely an American security agent. She finally catches up with Grey Fox and annihilates the entire squad minus Caxton, who is thought to be slain by Garcia (however, it later reveals he faked his own death); in order to stop her madness. In anger, she shoots Garcia, severely wounding him, she catches Garcia in her arms just realizing what she has done. From Benny's statement in a later chapter, it's implied both Roberta, Fabiola and Garcia came out of the situation alive. Whereas in the anime OVAs Garcia shoots the major, and then at Roberta "Killing" them, (using fake bullets) after she shoots him, he kisses her. Later she is seen in a stretcher and Rock thanks Garcia (revealing to be his plan of wanting to save someone)
In the anime OVAs, it is shown that Roberta, Fabiola and Garcia came out of the situation alive and well in the end. However, Roberta has lost one leg, one arm (for some reasons unknown, possibly due to infection), some fingers of the other hand and one eye. She is shown alongside Garcia meeting up with Shane, Fabiola, and the Japanese man's family.
It is ironic that while Roberta is one of the most powerful warrior-women, if not the most dangerous, in Black Lagoon, she is also humane. She is unwaveringly devoted to her master and dotes on his son, Garcia, whom she loves deeply. Her kindness can easily change as seen in a humorous omake in Volume 1 of the manga when Garcia slapped her butt in a playful manner, which prompted her to pinch his arm and lift him up off the ground by the skin of his arm as punishment.
In combat, Roberta is a truly fearsome opponent. Her strength, speed, endurance, and instincts have been honed to almost supernatural levels, so much so that Rock at one point refers to her sardonically as "a killer robot from the future" (a reference to James Cameron's Terminator movies), and she has extensive training in a wide variety of tracking, stealth, and combat skills, including martial arts and a very high degree of proficiency in the use of a wide variety of weapons. Among the weapons she has used is a Barrett M82A1 anti-materiel sniper rifle with a grenade launcher mounted underneath the barrel, which she could fire one-handed despite the weapon's size and significant weight - a testament both to her skill and tremendous physical strength. She has also used a combat knife, a SPAS-12 shotgun disguised as an umbrella, machine gun, grenade launcher hidden in a suitcase, spiked brass knuckles, trench spike, and twin Sistema Colt Model 1927s (see Colt M1911 pistols), as well as an antique flintlock rifle that once belonged to the Lovelace family. During her first visit to Roanapor, Balalaika deemed Roberta dangerous enough to not only mobilize all her soldiers, but to involve herself personally should the situation escalate.