Roommates

So, the boyfriend and I have had to move rooms for the next week or so. He technically isn't meant to be staying with me, but is. We have two other roommates and we're going to be getting a third one today (which means that my boyfriend won't still be able to stay with me :( ). Anyway, one of the girls has two of her friends staying which is fine, but....

Firstly, they have tonnes of alcohol in the room which is fine, but if the campus police were to find it we'd all be in trouble. Secondly, they're loud and noisy and in the room a lot. We came back last night and found one of the *guests* in our common room, on the floor with a guy, messing around. We went off to shower and came back to find an empty condom wrapper and an unwrapped (used) condom in the bin. I'm not a prude, but I think its a bit much to do that on the floor of a shared common room where you're a guest. Secondly, they woke us up at 8 with their loud talking and giggling. The boyfriend went out at 10 to ask them to be a bit more quiet, and they got better, but not much better.
I also went out into the common room and here was a guy out there, who presumably spent the night. I'm really annoyed at these girls (and our roommate who said they could stay) because they're really not acting with much decorum.

 I'm not entirely sure what to do. On one hand, I do have my boyfriend here and I guess he is a guest here. I have this other roommate coming back today, so I want to stay flexible etc because we might want to try to negotiate and get the others to agree to let him stay in the room. I also don't want to seem old and grumpy and like a party pooper. On the other hand, they're really not behaving with any decorum and disrupting our ability to enjoy reunions.

Does anyone have any advice? How would you all handle this kind of thing?