MPD is probably running on the Bryston? They would need to implement RoonSpeakers, but since they already have a BDP2 I wouldn’t count on it.
Chances are that PS Audio will include RoonSpeakers with their Network Bridge expansion.
enter link description here
You would still need a PC to run as Roon Core (maybe the NAS will be able to run it later?), so you might just as well use a fanless Intel NUC (or similar) thing and connect it to the DAC with USB directly.