The layer +Z Room Name is no longer with us. Dust to dust. Polvo a polvo. Room name objects in plan should go on the layer +Z Zones. This is the layer for zones of rooms. If you use zones, the stamp becomes the room name. If you don't, you can still use that layer for the object.
In passing, I will encourage you again to use zones.
Room names in section still go on +A Arch Note Reg Scale.