Ideally, for privacy, roommates' schedules allow each of them to use the dorm when they want, as they want without getting in each other's way. In reality, compromises and accommodations must be made. Suppose you study best in the evenings while listening to music, just when your roommate is ready to turn in. You might head for the library with your MP3 player and headphones. Meanwhile, your roommate might set out his clothes and books and fix his bagel and cream cheese for breakfast before going to bed, to slip out noiselessly the next morning while you sleep.
If you should be lucky enough to have a "private" bathroom, meaning you share it with only three to five other people, you may want to work out a similar arrangement for showering or putting on makeup. You might even put the schedule in writing.
Having guests in the dorm can also be a logistical challenge, with more schedules to accommodate. Fortunately, guests have dorms and sometimes houses of their own. So let them play host to pay you back.