You may well be right about USB ports. However, after having spent my share in various upgrades over the years, I have learned one lesson. When it comes to music play-back, let your ears, not the advise of others, guide you. And I stand by what my ears told me. I could not tell the difference between the direct connection to my DAC from the MacBook, and a high quality TT connected to the preamp and a good amp.
As for cost, I suggested getting a MacBook used. There are many to be had in the sub $ 200 range that will do well. It is simple, and just works, as opposed to rigging up a NUC and tweaking a Cubox, which is what a SE is, and ensuring that it is up to speed with the latest software and drivers that will communicate with everything else.
One more thing. Granted that a USB port is noisy, how is a local Ethernet network any better? Across rooms one is talking wire and connectors and therefore lots of interference. How exactly is this better? In any case, USB 5 is a good solution to usb noise and a relatively inexpensive device like Schiit’s Eitr offers such a solution.
I therefore stand by my advise: connect first with what you have – an old MacBook or a PC. Hear it first and give it a shot. If you really don’t like what you hear, then, by all means, go for the alternatives. Bottom line: trust the force in you (your ears). And remember – the point of it all is to enjoy the music. Roon, for me, is about the integration with lyrics, and the discovery. Have fun with that.