In Roon’s early days, I would have sworn it sounded inferior to Mosaic/UPnP (I may have even posted as much here on dcs.community).
During the Covid19 lock-downs in 2020, partly driven by a debate with Martin Colloms (HiFiCritic), I found the time to set-up an objective testing methodology that completely removes any subjective opinion or biases in evaluating whether or not there’s a difference between Roon and Mosaic (though originally intended to debunk Audiophile Ethernet Switches/Cables, which it also does quite well).
On the hardware side, the setup requires a Vivaldi Upsampler & Clock, and a PCM Recorder; one that can receive a PCM stream and record it, like the TASCAM DA-3000, which has the added benefit of being able to be externally clocked to the same clock source. So, all comparisons are done in the digital domain where there’s no chance of analog noise causing capture sample variations.
On the software side at the time I used Audio DiffMaker which compares two PCM .wav files for any differences. These days there’s also the DeltaWave Audio Null Comparator which does an even better job.
Using a single source file played back through various ways, in this case Roon vs. Mosaic, and the digital outputs from the Upsampler captured, one can then compare the captured .wav files and generate a difference, which you can then listen to for any audible variances, or view with something like Adobe Audition right down to an individual PCM sample.
When the tests are done correctly, you’ll find that the difference between the captured streams is null 
