to allow an item, object, or being to warm up to room temperature, or become less cold, not to desire it to be warmer than room temperature
My barley wine is too cold, it needs to room up.

It feels great coming in from the cold, i cant wait till i room up.
by ransemvstheunman July 28, 2009
Also in short text "r^" is a term used in the video game SOCOM to notify other players that the room/server they were waiting on is now up and ready to join. Usually said when organizing a clan battle to make a designated private room with a password.
"Hey guys, Room Up! Hurry and join so we can start the game A.S.A.P."
by Jay Ping Quan July 21, 2009