Can these floors be used over concrete with in-floor heat? And if not, do you offer flooring that would be better used for this?

You can install our 1/2" Mega Rubber Rolls over a concrete floor with in-floor heating. The rubber flooring will not melt. The only thing you will notice is that you won't get the full effect of the floor heating system. These systems were made for porous materials like stone and tile. Rubber is a decent insulator, so you will only get some effects of the floor heating system.