Interesting, I have the Pro iDSD also and noticed the same when I was first using RoonBridge (Allo USBridge), with Roon DSP disabled. That’s just 2 weeks ago, with mostly Tidal CD quality streaming.
I have no issues when using Roon --> HQPlayer NAA (same Allo USBridge) though and that’s how I use the Pro iDSD now, so I haven’t been in a rush to report the issue to Roon.
But seeing your post reminded me of the first few days when I was using Roon exclusively with Pro iDSD, a couple of weeks ago.
Personally I didn’t want to say it’s a Roon specific issue immediately - I didn’t test Audirvana to USBridge to get more info, because I moved quickly to HQPlayer after getting Pro iDSD.
I might test on the weekend, before I say it’s specific to Roon in my system.