If all else fails go here and purchase that poster for yourself. Or make your own if you want. But listen here, do you really think your stranger roommate is going to constantly abide by these rules? It's all fine and dandy to say "hey roommate, overnight guests only once a week", but people who have just gotten away from their parents rules will not likely be keen to follow yours.
You can give the 'overnight rules' your best shot. But if your roommate feels like breaking the rules once in a while, then they will. You can report them, but that will obviously cause tension. If anything you should make some 'get out of jail free' cards (like 5) for when your roommate or you break the rules. If all 5 cards get used you agree to not have any overnight guests for a month. Then when the month is over, you decrease the 'get out of jail free' cards to 4. and so on and so forth.
And just a note, if you've ever heard your parents 'making love' in the room beside you. You'll know that sometimes people think they're quiet when they're not. And you should be ready for this with any overnight guest. Hence the earplugs being a good investment.
Again, I'll let you know when I get there. But from my prior knowledge and acquired life skills, it's better to be safe than sorry.