On top of my very heavy and kind of odd latex mattress (weighs a ton; there's a long story but my ex ended up with three of them so gave me one) I have a 2-3" topper, and all of that is held in place with a mattress pad with elastic sides that reach down around the whole thing, much like a fitted sheet does.

Over the years as a seasonal park ranger I moved around and had a foam pad (5-6" thick) that would roll so I could pack it with my other few belongings in the back of my pickup. It went out on the floor, no frame involved, but all things considered, was very comfortable to sleep on.

The roof gets inspected tomorrow morning and shortly after that I'll have a plan as far as new roof or no new roof.