In my opinion, It's going to be a bit problematic.
The Rizomas actually replace the stock throttle tube (normally covered by a grip) with an integrated grip and throttle tube.
So those heating pads are going to have to fit inside the throttle tube/grip and be subjected to constant rubbing between the twisting throttle and the handlebar. Which in turn seems like a sure recipe for wearing down of the insulation followed by a short circuit.
Maybe (and this is a big maybe) if you glued the heating pad to the inside of the throttle tube and also wrapped the handlebar with some sort of Teflon (plumbers' tape?) you might be okay. But even then, that seems like a tight squeeze.
Still, nothing ventured, nothing gained
Try it out and check periodically to see if there's any wear on the heating pad.
Mind you, this is all for the throttle side. Your left hand should be toasty with no problems as you should be able to squeeze the pads in between the grip and the handlebars on that side.