When I had roomies about 2yrs back I was rooming with a couple that had really loud sex. (their room was next door). I knew he had a big dick (because of some of their convos..they talk loud), so it was hot to imagine. I found it insanley hot at first, but honestly 3-4 times in, you sort of get bored of it..and it just becomes annoying.
I think at some point when it comes to exhibitionism/voyeurism, you always want "more".
I shared a room at the frat house for two years with this guy who would jack off every morning with me sleeping just 8 ft away (in the same room). This guy also had a very big dick that I know (from sucking it) was over 8 inches.
It would give me an instant erection being awakened to him jacking off (especially the heavy breathing and convulsions as he would ejaculate) but it became annoying.
It was a little weird bringing it up to him (since it was almost six months of this before I talked to him) but I told him that I was being awakened every morning by him jerking off, and could he please do it in the bathroom (which was just next to our room).
He apologized, and then only jerked off with me in the room when he had been drinking or very stoned (which was normally after a frat party) and he probably thought I was deep asleep (or was hoping I would blow him).
BTW, he is now married with a kid, and claims to be 100% straight. However, I seriously doubt this percentage since he ask me to blow him several times (which I did) and he also blew me but every time he ask me, he was either very stoned and / or had a few drinks. He always acted like he did not remember (being that he was so wasted) but I am sure he did. We are actually still good friends but we have never been physical since sharing the room together.