Very little is known about Agent Rothman; he only appears in the Texas Chainsaw Massacre: The Next Generation and is never mentioned in any of the other movies. He is first seen when he enters the Sawyer family house and he tells Vilmer Sawyer to 'show the true meaning of horror', he also displays predatory behaviour towards Jenny (Renee Zellweger), licking her face, these facts could suggest that Rothman is in fact Vilmer's Boss, and that although he seems deranged, he seems to show a slight amount of remorse for Jenny, at one point, implying that Vilmer was doing the wrong thing by capturing Jenny.
He is next seen when Jenny is being chased by Leatherface and Vilmer. He arrives on the scene in his car, unbeknownst to Jenny. When she gets into the car, Rothman tells her to relax, that there is nothing to fear. He apologises for his earlier actions, though Jenny understandably doesn't believe him and says 'Fuck You'. Despite this, it seems that agent Rothman dropped Jenny off at a police station, then, he is never seen or heard from again.
Rothman is perhaps the most mysterious character in the Texas Chainsaw Massacre series; he wears much more upper class clothes, and has strong elocution. There have been many theories as to who Rothman may actually be. Some believe that he has a firm objective similar to that of a terrorist, but without capturing innocents. Some also believe that he might actually be an undercover FBI agent, hence his mysteriousness and impeccable dress sense.