In technical terms, a roommate is someone you share a bedroom with, while a housemate is someone you share a house or apartment with. However, in the United States, people often use the term roommate, or roomie, to refer to anyone you share a living space with, even if you're not sharing a bedroom.
A roommate is a person with whom one shares a living facility such as a room or dormitory except when being family or romantically involved. Similar terms include dorm-mate, suite-mate, housemate, or flatmate ("flat": the usual term in British English for an apartment).