You use the Roon app on a phone, tablet, or computer to tell the Roon Rock server (the NUC) what music to stream and where to stream it.
Any "Roon Ready" device connected to the network (via WiFi or ethernet) can receive the streamed music. Once the NUC is set up, you can stream any number of devices on the network.
About the cheapest Roon Ready device is a Raspberry Pi running the free Ropieee software.
A better option would be a WiiM Pro Plus with coax output.
And even better would be a streamer like the Hifi Rose, Eversolo A8, or many others.
I've found that using Roon to run things is 10x better than the clumsy software that a lot of these streamers, even the expensive ones, come with.
I use an iFi iSilencer on the ethernet and run the switch on an iFi iPower Elite.
Realistically, there are lots of sources of EM noise on cabling that can exacerbate inherent jitter in digital. Alpha Audio has done a lot of tests and comparisons of streamers and noise in streaming:
https://www.youtube.com/@TheAlphaAudio/videosAlthough I have sold off my main system for a move, I have become interested in Streamer/DAC/amp devices where the designer can mitigate the jitter from input to DAC. I have not heard the Axxess Forte, for example, but it's an interesting approach:
https://audiogroupdenmark.com/product/axxess-amplifier-forte/My main system had been a Holo May KTE DAC, Holo Serene KTE preamp, and Pass Labs or Benchmark amps. So, I've always assumed that separates each optimized for a purpose were better, but I'm trying to keep an open mind as technology evolves. A new main system is a while away, so for now it's just browsing the shop windows.