The 26-year-old actor - who was left heartbroken in July after his girlfriend and co-star was caught cheating with married Snow White and the Huntsman director Rupert Sanders - has agreed to be "professional" and attend the Los Angeles screening with Kristen in November, because he is worried about how fans will react when they see the actress.
A source told The Sun newspaper: "He has told movie bosses he'll walk the red carpet to save her from embarrassment and any female fans booing her."
Robert 'not interested' in speaking with Kristen
Although Robert has agreed to fulfill his commitments to the movie franchise - in which he plays vampire Edward Cullen opposite Kristen as lover Bella Swan - he is said to be "not interested" in speaking with the actress, which is causing problems for film bosses.
An insider commented that Kristen really wants him back, but that Robert is not interested in talking to her right now and that is certainly making things difficult for the plans on doing any press together for when Twilight comes out.
Kristen, who is believed to have had little contact with Robert since the scandal unfolded, recently pulled out of the London premiere of her new film On The Road because of fears of a backlash from fans of the British actor.