I think it's hard to broach the subject of "rape fantasy" but really, how hard is it to get a bit rough? I've never had a problem with pinning, or throwing them on the bed, or pulling their hair etc. I think if a girl responds negatively to that, sex is going to be horrifically boring, so what's the point anyway?
I've never had a girlfriend with a history of being raped though, so I appreciate that situation is completely different. Obviously if you're married the solution is NOT divorce, but if I got with a girl that went cold with me the minute I got a bit rough I wouldn't stay with her for long.
My advice: Make sure the sex is spot on before you get married. Sorry.