Is there another bit of software that allows me to integrate a streaming library and local/ networked files pretty seamlessly, decent EQ and multi zone playback?
There probably isn't a single purely software based solution comparable to Roon. JRiver comes closest perhaps although the UI is admittedly pretty fugly. Many people seem happy with Plex although I don't have any experience with that.
As noted previously I have the NAD C658 running BluOS which does a decent enough job for local content and (on the rare occasion I listen to) web radio. When evaluating Roon I was also subscribed to Tidal which I have also since dropped. Spotify's library and discovery features are far better and sound quality is indistinguishable to my ears. Thus Spotify is the only streaming service I subscribe to and, since it doesn't integrate into any 3rd party services there is even less point in Roon. I don't have need of multizone so can't help you there.
Any of the little SBC based streaming boxes (Rpi, Odroid, etc.) running Moode or Volumio do as good a job for local and streamed content and have useable interfaces. They can all run Spotify connect as well.
For many years my primary 'media center' was OpecElec/LibreElec on an Odroid C2 and more recently OSMC on Vero4K which are all Kodi (formally XBMC) based. Kodi is primarily used for locally hosted movie playback but is perfectly fine for music too and has excellent library tools, phone/tablet apps etc.
EQ is more tricky on Linux based devices. For my 'headphone rig' I'm using Brutefir in Volumio which, once you get it set up, works fine but is admittedly a bit wobbly. Moode is more limited with only a four band parametric EQ. For my speaker setup I have Dirac on the C658.