There are a lot of reasons to use Roon, and people use it for different reasons. But one thing everyone wants is best possible sound quality. However, as far as I can see (or hear), there haven’t been a lot of work in this area lately.
One way to partially solve this is to support VST plugins (especially now with Dirac requiring a VST host), but that seems to be a dead issue. A separate VST config program that has to be run locally with headless use in an endpoint would be enough The config app could even be a web app provided only the generic VST properties are shown, which would make it easier to integrate to ROCK and Nucleus.
Oversampling is also very basic. SoX in JRiver sounds better, not to mention oversampling in HQPlayer which probably has 10 algorithms that sounds better than oversampling in Roon.
And playing music locally from Roon sounds slightly worse than from Audirvana, which might (or not) have something to so with the rich GUI Roon has.
Finally, while the convolution engine seems fine, the PEQ could be improved upon. It does not sound as good as the best VST PEQ plugins out there like FabFilter Pro-Q 3 (which also has a very nice GUI).
Don’t get me wrong, the improvements to Roon lately has been nice, but I think some effort should be on improving sound quality, especially VST support and improved oversampling.