Hi,
I bought an Intel NUC, a tiny, silent computer, which I connected to the home network. It had the Roon software preinstalled, and also has internal storage for downloads and ripped cds.
This was much cheaper than the Roon Nucleus and of equal performance. I leave it on all the time though I can reboot it through the network.
I imagine ARC could not work with the NUC turned off but I have never tried that.