Athlete's Foot does refer to a fungal infection of the skin of the foot, usually affecting the area between the toes. It is characterized by changes of the skin that can include redness, scaling, flaking and itching.
The same type of infection can occur in other places of the body as well (for example, jock itch when the infection occurs in the groin). The fungus is usually contracted as a result of walking barefoot over a moist surface such as a shared bathroom, locker room or common shower. If your roommate does have Athlete's Foot, then it is possible that the infection could be picked up through the use of a common area.
t would be advisable that you wear some flip flops in the shower and bathroom to help reduce your chances of getting the same infection. Fortunately, there are a number of very effective medications available over the counter that can be used to treat Athlete's Foot, such as miconazole or terbinafine.