If you are using headphones, headroom DSP helps. I have not tested.
Sample rate conversion to DSD helps if your DAC supports it. Tested to highest PCM sample rate (my DAC does not do DSD) but could not find any diff. Reverted.
Roon automatically scans the underneath audio hardware and picks the best possible supported settings. Apart from that you can play with DSP filters but they can create more trouble than refinement if not done carefully.
The default settings are usually the best. If you want to tweak them, try disabling "load on boot" and mp3 encoding options. They can't be disabled in trial mode but I would highly recommend it for the full app anyways since they're only trial versions of what might otherwise be an excellent feature set.
I honestly think this is a gimmick that was hyped up when its release was announced; I wouldn't advise people to install something where these tweaks are on by default until more people have tested or tried out the non-default features and provide feedback as to their experiences with them and whether or not there are any meaningfully different effects at play between the factory settings versus what those tweaks achieve if any objective difference.
For me Convolution filter support helps a lot. It supports raw, wav or zip files. One can also use REW profiles.
Convolution filters help correction of frequency & impulse (timing) response in my system which has the maximum impact than any other feature including upsampling.