Lots of things have Roon features. For example scrolling lyrics exists in many apps, and audio zones are controllable by Sonos, and mpd/upnp have solutions that run on raspberry pi.
Given that, Roon does provide a lot in one place. If you continue down that line, I’d throw in some other stuff even if its not all truly unique:
- composer -> composition -> performance
- file and streaming combined
- roon radio is actually good, and the thumbs up/down is a good way to built up playlists
- “add to library” feels like a shopping spree, as opposed to just starring something
- album versions
- user profiles so your kids/spouses plays do not muck with your history and/or recommendations
- signal path
- streaming dsd
- easy to use dsp
- support for multiple streaming audio protocols so you buy devices for their capabilities and not their compatibility
- the best mqa support (reapplying render bits post-dsp)