I'm running Roon Legacy on a hand me down 2011 iMac connected to the network via an ethernet cable into a TP Link Mesh satellite; it's on a bookshelf in a spare bedroom so doesn't take up any space.
With a decent internet speed I've had no issues, Roon delivers music instantly to my iPad, phone and laptop with EQ applied as needed but then I don't have DSD files with insane sampling rates or a need for HQ Player.
Out of curiosity I used an easy to apply OS patch to enable it to run Catalina ( High Sierra was the limit for the 2011), so I could now install Roon 2.0 but I have no use for ARC so will stay with Legacy as long as there are no more compelling reasons to upgrade.
You're right not to splash out on Roon hardware, it makes more sense to buy Lifetime than to pay out for a Nucleus or even a NUC;
I now realise that a strong wired network connection is more important.