Having just completed a Roon trial, I can confirm that the SQ is better from my Zenith Mk3 (v2.2.3) than when Roon is enabled. This was running with the Zenith as the Roon Core.
However, what did tempt me to persist with the Roon was the provision of DSP. We all like to think that our perfectly balanced systems should sound perfect with every recording, but of course that's not true. Even the best system in the best room occasionally requires a little equalization. The parametric equalization is pretty good - though detail and transparency does suffer.
I had additionally been suffering sibilance, so tried buying a MiniDSP UMIK-1 microphone and generate a convolution setting using REW. It didn't help really, and just seemed to cause excessive clipping with some tracks, unless I applied a -6db attenuation - which for every other track just resulted in much lowered output.
Roon does offer many features, though most to me seemed excessive.
My lesson? Innuos's OS is simpler, has a purer path and sound quality, and has enough features to allow easy music selection. And it's free. If they could include a simple parametric equalisation option that doesn't impact SQ then it would be perfect.