Roon Nucleus quality as a network streamer

I've considered the same. Currently just using a very old MacBook Pro for Roon. Would the Roon Nucleus be that much better or how about the Roon vs Small Green Computer?

Im running The Roons (TR) core on an SGC ST i5 and like it very much , Qobuz as source. . I was originally running just a Bryston BDP Pi with MPD. I first added TR on a iMac. My network consisted of Linksys Mesh with 3 nodes. Node 1 hardwired to modem, iMac hardwired to Node2 and Pi hardwired to Node 3. initially MPD on the Pi sounded way better than The Roons with the Pi as an endpoint. Then I added the SGC ST and hardwired it to Node three and then ethernet to Pi, also upgraded to cable to CAT6. Now TR sounds very close to the Pi/MPD. Pi/MPD still has just a smidge better sound stage so I switch back to that for critical listening.

If I was investing from scratch and I had to have TR I would explore the SGC Optical Rendu solution.
The one really cool thing about TR is you can use old Sonos connects as endpoints (16/48 only).  I got one out in the garage form my shop and one on a HT setup.  You can find those old connects for cheap on craigslist as they are being aged out of the Sonos ecosystem and people are dumping them. :)