I am thinking that I would use underfloor electric heating in the winter. Can I put this under tiles? Will they still fit together and lie flat? Or is there another way to use the underfloor heating with tiles? Or would rolls be better?

You can install floor heating under our 3/8" Sport-Lock Rubber Tiles. These tiles will not be affected by the use of it. Since rubber is an insulator, you may not feel the full effects of the heater like you would with tile or concrete. In regards to the installation of the floor heating system, we would recommend following the install instructions that accompany the system.