ROCm is not spelled out anywhere in their documentation and the best answers in search come from Github and not AMD official documents
"Radeon Open Compute Platform"
https://github.com/ROCm/ROCm/issues/1628
And they wonder why they are losing. Branding absolutely matters.
That, and it only runs on a handful of their GPUs.
If you are talking about the "supported" list of GPUs, those listed are only the ones they fully validate and QA test, other of same gen are likely to work, but most likely with some bumps along the way. In one of the a bit older phoronix posts about ROCm one of their engeneers did say they are trying to expand the list of validated & QA'd cards, as well as destinguishing between "validated", "supported" and "non-functional"