Two different Hydra Z's... neither worked with my Mac Mini

I’m pretty sure Roon will ignore your Audio MIDI settings. They’ll be fine for iTunes, though (subject to MacOS limitations).

FWIW, this sounds to me like (1) a problem with user settings in Roon or, less likely, (2) a hardware problem with the DAC. Maybe start a new thread about this problem and post screen shots of all Roon settings related to playback via the Hydra?