The official Roon Core device, the Roon Nucleus, is available for around £1,500 I guess. A self-made NUC system with ROCK is already a bargain IMHO. As ROCK is a stripped-down Linux optimized for running a Roon Core on supported Intel NUC hardware, you might find that some things wont work on an AMD based system but you’re free to try it.
Before you ask: No, I don’t know of specific things that wont work right away.
If there are no other needs and you just want to run Roon Server on that machine then I’m unsure if the £ 100 saving is worth the hassle.
Notes: ROCK on a supported NUC is fully supported by Roon Labs whereas MOCK builds belong to the Tinkering section of this forum and you may have to figure things out for yourself or with the help of the community should you run into problems with your setup. The costs for a working network and/or graphics adapter or a Windows license might easily eat-up the initial saving.
This write-up is not a general advice against your plans, it should just make you aware of some points you should include in your personal risk analysis if not already done so.