A
person who is a
roommate, but- separately from that- is also a friend.
A
person who you would call a "roommate" because they live with you, AND a "friend" because they are actually a good friend of yours.
Used to specify that your roommate is a good friend of yours.
1: "Hey, this is my friend,
Jim."
2: "Isn't he your roommate?"
1: "Yes. But if I call him my roommate, you'd not be lead to believe we're good
friends, apart from living together."
------------------------------
1: "Hey, this is my froomate,
Jim."
2: "Hey Jim, nice to meet you."