@barts
Like you, I also have the Bryston BDP 3.0 / BDA 3.0 set up - and find the convenience and sound quality amazing - using the Bryston Manic Moose software.
And... like you... I do not understand how the BDP software can affect the sound quality in any manner.
So... I’m also very curious... as to how Roon, or any other BDP software, can have an effect on the sound quality of what’s being processed by the DAC. It would seem that the BDP software is only providing the digital file to the DAC and that "bits are bits," no matter how they’re being transmitted to the DAC.
So... count me among those that may be skeptical that there is any difference in the sound quality of a digital file until it is processed by the DAC.
Hopefully - there is someone here who has enough engineering knowledge to provide a rational explanation.
Though, I suppose it could relate to how quiet (noise free) the BDP is - some may well be quieter than others, and the interface cable can certainly make a difference in the sound quality (AES/EBU vs USB, etc.). So... I wonder if that is actually causing the difference in sound quality some are noting between software products.