You've already got an amdgpu driver in your kernel. Possibly an old one but it'll be there. ROCm is userspace.
CUDA PTX is that Intermediate Language representation that's portable for cross platform usage but I'm not exactly sure how that is implemented for Blender 3.0/later.
P.S I have Ryzen 3000/Zen+ series APUs and Vega Integrated Graphics on 2 systems and the laptop has Ryzen 3550H/Vega 8CU iGPU and Polaris Radeon RX560X dGPU while the Mini Desktop PC has Ryzen 3400G/Vega 11CU iGPU only.