Lumin U1 mini vs SOtM 200 neo ultra as Roon endpoint

If your priority is sound quality you may want to reconsider Roon. 

Agreed - Roon interface is awesome. 
As to streamers - I had the U1 Mini and it’s a good sounding machine for the money. With it you have flexibility to use Lumin native app, Mconnect, Roon, Jplay. I would strongly encourage you to try it all and determine what sounds best to you. Advantage of Jplay is it doesn’t need a computer to run on and has a really nice interface. Lumin app is pretty bad from the UI standpoint 

Then I’d recommend going with the U1 Mini. Get a good USB cable and you’re all set. 

Try both coax and usb but money’s on usb sounding better.