well ROCM is supported in Linux https://rocm.docs.amd.com/projects/install-on-linux/en/latest/

I've installed it on my (single) AMD GPU (I thought it was for something else) on EndeavourOS (which is, obvs, arch btw :D).

I've been using endeavourOS for about 1y now, after a few years of Mint (and 20years of everything else. Yes, I've used gentoo as well back when it was only install from stage1). It does feel faster (on the same hw) but I've never done any real benchmarking, so it could be just "new shiny feeling faster". I've found an article a few weeks ago comparing boot/compression speeds of different distros. In your particular case I wouldn't be using Debian as I feel you'd need quite up-to-date drivers, and Debian is conservative (and that's a good thing personally, I use it on my servers).