like the others have said anyone in any cabin can request a robe, just ask your cabin steward for one. If you use it, you will get a fresh one the next day. You can purchase them to take home. You will be charged for the robe if you attempt to take it home without purchasing it.
The robes are nice and warm, especially after freezing to death in the rest of the ship! Too bad you'd be embarassed to wear them when you go to dinner or a show! Maybe that would give them a message to turn off the arctic blowers! HaHaHa