Roberto is a criminally-insane robot invented by Mom's Friendly Robot Corporation. He's known to to repeatedly rob the same bank over and over again, and carries around his trusty "Stabbin' Knife".
In "War of the Villains", Roberto stormed Planet Express to get some answers on who killed his mother and mother to robots everywhere. He interrogated his former pal, Bender, for answers, who told him that Mother Gothel killed Mom. Intrigued, Roberto decided to plan out his next move.
Later on, when Gothel would return to Rapunzel's Tower, she saw Roberto with her quote-unquote "daughter" bound and gagged. Gothel tried to get Rapunzel out of Roberto's presence, but Roberto took out his Stabbin' Knife and rush toward Rapunzel's Hair, the source of Gothel's eternal youth. As Gothel began to age older and older, Roberto became frightened and jumped out the window. Needless to say, he survived, but damaged one of his eyes.