How to be open and honest with my roommate/friend?

My roommate and I have only known each other for a couple of months but already we are fast friends. One regard in which we differ is that she has a lot of male "friends", during first semester she went out to see them and slept at their houses so I knew about it but wasn't really exposed to it. This semester she comes home with different guys at least twice maybe three times a week. They aren't having sex to my knowledge, but they do other things. she usually brings them in pretty late so its not really a problem except sometimes I wake up and hear them going at it. I am not sexually experienced and I have never had a boyfriend that I've been intimate with. I consider the room a private sanctuary and what she does makes me so uncomfortable hat I'd rather sleep out in the hall. I don't really have any other place to go to sleep. I don't want to lose her as a friend and there is no guarantee that if I got another roommate she wouldn't be doing the same thing or worse. Does anyone have any advice on how to address the situation?