Writers Guild Italy talked to Brady & Mona about the film, and Rob.
I have only posted the part where they talk about Rob, the link to whole interview is at bottom of post..Slight spoilers be warned!

And with an actor as Robert Pattinson? I know he really looks forward films that are author film, that offering something else out of the mainstream.
Brady: Yes for sure, he is a real cinephile. There is so many actors that could use their celebrity in a really amazing way, like Will Smith or Tom Cruise… Well Tom Cruise does that sometimes. There’s a lot of people who really don’t take advantages… Like I can get somebody’s film made and they are gonna challenge me and we are gonna grow together.

Did he help in financing?

Brady:Of course. The thing is funny because at the time… he was cast several years ago, we had no idea how significant it would end up being. We had a lot of others fancy cast members at one point, but at a certain point he was the only way to get the film made, after many years was to have Rob involved. And we originally hired Rob because of the fact we wanted somebody really CHARISMATIC and really RECOGNIZABLE.
Mona:We wanted to feel right the way that this character is very important.

Brady:The thing great about Robert is that the less he does.. YOU CAN'T TAKE YOUR EYES OFF THE GUY! BECAUSE HE IS BEAUTIFUL TO LOOK AT, IT'S REALLY LIKE HE DRAWS YOU IN, IN A CLASSIC COLD WAY. HE IS COMPELLING.

Even with the shaved head…

Brady:Yeah!

Do you think some of the Twilight crowd will go to see the film just because he is in it?

Brady: I don’t know… They go see Cosmopolis?
Mona: I think it would be good for them.

Source & link to whole interview..  http://www.writersguilditalia.it/scrittori-a-venezia-brady-corbet-e-mona-fastvold/
Via: https://twitter.com/sallyvg