If you are cruising on a RCCL ship they do not have self serve laundry rooms or irons in the cabins. If you need something pressed, they do offer a laundry service, just let your cabin attendant know what you need.
You will not find irons in any cabin on any cruiseline. Irons are a fire hazard and ships are very concerned about that type of possible problem. Some lines have ships that have self-service laundry rooms that have irons in then attached to the wall so they have to be used there but RCI is not one of those lines.