Oh a inflatable mattress also violates the Fire Code but Disney does not know about it. If you could rent a roll-away twin bed from somewhere, and have it delivered then Disney knows about it. It is not about room capacity.
What size Villa are you trying to put a roll-away in, and where do you think you would put it?
For example an inflatable mattress is often used at the Value Resorts, and the space it blocking the door to the room, a Fire Code violation.
What size Villa are you trying to put a roll-away in?
Dave