If my roommate has either a stomach virus or food poisoning, how do i prevent from catching it? how likely am i to catch it? our room is really small.

Meticulous cleaning: Viral gastroenteritis is highly contagious. Wash your hands frequently. Wipe surfaces with a disinfectant liberally and wash sheets. If you think you've washed your hands enough, wash them one more time.

contagion: Wash your hands with soap and water, or use hand gel like purell. Avoid using any clothing or towels that she has used. Don't share utensils or glasses while eating and drinking.