If you don't want to be responsible for laundering and/or replacing your roommates' sheets, make sure their bedroom doors are locked. With all of the fun you'll be having (and booze you'll be chugging), there's no way you can give every guest your undivided attention. If you don't lock the doors to the rooms you need people to stay out of, there's no way to guarantee that your friends won't turn your roommate's bedroom into a ramping shop. You need to keep your guests contained to one area to ensure that no one is popping a Molly and sweating on your sheets, or having a threesome where your roommate sleeps. Unless that's the type of party you want, in which case, rules won't apply.