This is just my opinion (no science to back it up), but I think heated roosts are just a gimmick dreamed up by the folks who sell stuff to bird owners, are unlikely to be of benefit to the birds, and could actually be harmful. Parrot owners are frequently targeted by this marketing, too. A heated perch is completely unnatural to a bird. It's not like a reptile who naturally seeks out sunwarmed rocks to rest on.
The risk I see is if the bird has no where else to perch they might become overheated from perching on the warm roost. Heat is transferred most efficiently through the feet, since uninsulated by feathers. And then there's the issue of malfunction: what if the device doesn't perform as it's intended and gets too hot, gives a shock, etc.
At best, you're spending money on something that is of no real benefit to your birds, and at worst, you're spending money on something that might actually harm them.
If you want to provide supplemental heat, I'd look for a different way to do it than a heated perch.
