I like the processing functions, which I use Roon to play both, my local library as well as streaming Qobuz. For both, my speakers and headphones, I use it to apply Album-level ReplayGain to everything, so it minimizes the need to adjust volume (I listen to a lot of mixed-track playlists, rarely play through complete albums). Additionally, for my headphones, it has an excellent Crossfeed function. I also use the in-built PEQ for very tiny adjustments to my headphones, and for my speakers, I have a special Late Night PEQ Profile which essentially applies a fixed, Fletcher-Munson-style adjustment so that when I listen after my kids go to sleep (their room is directly on top of my speaker system) at only 45-55dB, it remains as clear as when I listen (without PEQ) at daytime levels (65-75dB average).
Roon itself is very content-oriented so it brings up really interesting stuff about the artists and the albums, which I frequently will read while listening.
-Ed