They're called "roommates," but I think a more apt title is "room-sometimes-acquaintances-sometimes-quiet-cohabitants-sometimes-straight-up-enemies." Doesn't quite roll off the tongue, but it's a little more accurate for someone to whom you leave bonkers, passive-aggressive notes instead of, I dunno, talking.
To be fair, when it comes to roommate communication, I'd take a strange note over a strange incantation. A strange note, you read it once, get a little mad, go on with your day. A strange incantation, your arms become frog legs, you start floating, you speak in tongues. More inconvenient, you know?