I have a trmpurpedic bed and have notice LO can not and really does not roll/move around on it. When she is on her tummy time mat or in her crib she moves around like crazy.
LO is a mover as well and doesn't move much (but tries) on our mattress. It isn't a Tempurpedic but it does "sink" in, and he has difficulty rolling from there.
I love love love our tempurpedic! And same thing, lo doesn't roll around on it (which I like!) But it has been an awsome place for him to practice sitting up on his own.
Re: Tempurpedic beds