Not on the ROCK approved hardware list, but I’ve had great luck with these. I set one up for my nephew and another for my nextdoor neighbor. They are both now happy Roon subscribers as a result!
https://www.amazon.co.uk/GMKtec-Desktop-Computer-3-60GHz-Business/dp/B0DFWPX1P8/
Easiest ROCK builds I’ve ever done. Simply flash a thumb drive with the Roon OS factory reset image using etcher, connect power, network cable, HDMI display or TV, and USB keyboard, and follow the prompts to complete the installation. Then shut it down, connect it to your router and power and job done. (Optionally, you can install codecs.)
I posted about this a while back here: MOCK Success Report - GMKtec Mini PC N97
As this is technically a “MOCK” build, the hardware is not officially supported, but so far, so good.