Keep Food Locked Up
It's unofficial dorm room protocol to hide the better parts of your personal food stash. Even a courteous roommate can have freeloader friends. But no matter how well you hide your snacks from people, they might not be safe from pests.
Mice (and rats, too!) can chew through cardboard and cellophane. If they're really desperate for their next meal, they can even nibble through slightly thicker plastic, such as those inexpensive reusable food storage containers. Keep as much food as possible in your dorm fridge; everything else should be stored in sturdy, heavy plastic containers. Decorative metal tins are even better.
It's generally advisable to avoid charming, homey touches like candy dishes and fruit bowls. Fresh flowers, unfortunately, are prone to the same misfortune. Their presence is like inviting ants and mosquitoes to a picnic. It's hard to advise against something as cheerful as a bouquet of carnations, so perhaps a bit of lenience is in order. Check flower vases and potted plants frequently for signs of insects, and toss it when it starts to wilt.
College students should be experienced enough to know this, but we've seen otherwise, so here goes: Food trash should be thrown out immediately so it doesn't attract flies. (Plus, formerly-edible garbage gives a small room a telltale funk that's hard to erase).
If you keep your consumables under control, pests will get the message that you're not willing to share.