ROCm supports current gen consumer gpus officially and a decent chunk of recent gen consumer gpus unofficially. Not all of them of course but a decent chunk.
It's not ideal but I'm pretty sure CUDA didn't support everything from day 1. And ROCm is part of AMD's vendor part of the Windows AI stack so from upcoming gen on out basically anything that outputs video should support ROCm.
No, but CUDA at least supported the 8800 gt on release [1]. ROCm didn't support any consumer cards on release, looks like they didn't support any till last year? [2]
It's not ideal but I'm pretty sure CUDA didn't support everything from day 1. And ROCm is part of AMD's vendor part of the Windows AI stack so from upcoming gen on out basically anything that outputs video should support ROCm.