Rudi, it’s actually trivially easy to prove for yourself that Roon is bit perfect transport from source file all the way to the DAC:
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Create a single pure-tone PCM .wav file of whatever frequency you fancy - 1kHz probably works best.
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Use Roon to playback that track and capture the output, either as PCM out of the Upsampler (in Clone mode), or as an analog recording of the DAC output.
You’ll see it’ll be perfect.
There are other (slightly more complex) ways to do the same thing, even with music files, and utilising Roon Bridge on a PC/Mac. But all of them will just prove that Roon is in fact bit perfect 