I use a NUC because it was cheap, easy to set up, and most importantly for me, Roon provides a free OS for NUCs called ROCK.
Mine is a NUC7i3BNH an it is nearly silent. I don't use it for anything other than the standard Roon Core duties of storing and serving up my modest library. Others on the Roon forum use their's for things like DSP and DSD conversion so they have more powerful NUCs. Those are nosier apparently which makes sense since they have to dissipate more heat from the same size of computer.