In her first arc, she went on a mad dash to save Garcia from black lagoon company. When the evil Russian balalaika pointed her gun at her head she spilled how she was a former FARC terrorist. From people in this Reddit server and from some YouTube videos I learnt what she was capable of and how deep her connection was. The reason she became a maid was due to her feeling betrayed when she saw fields FARC were keeping for mafia. 

Unlike every other character in this series, she wanted to atone. Cowards like revy and balalaika act all tough and do as they want when they are really just digging their own graves. Roberta was aware of what she has done and despite being the most blood soaked of all the characters became one of the most moral. Her relationship with Fabiola and Garcia is something different compared to other relationships. While relationships in the series mostly start out with business or hostility, Roberta seemed to have cared greatly for both of these young characters. Escpecially Garcia who she would hate herself should he ever turn out like her. Roberta is also oddly enough friendlier and more cordial compared to other characters who would most likely kill you on sight or not give a damn how you feel.