The PS Audio Bridge II firmware gets updated by PS Audio. A new update is scheduled for next month by PS Audio. BTW, if you haven’t updated your DAC to Huron already you should seriously consider doing so. It’s available on the PS Audio web site.
Roon Ready devices do not use Roon Bridge internally. They are updated by the manufacturers.
In general, we have designed RAAT to maximize what we can deliver without requiring firmware updates on the actual devices since these are really difficult to accomplish with so many vendors involved.
From the release notes for b234:
This change rolls out as part of the update to your Roon Core–which will use the new protocol when speaking to all RAAT-based zones. Aside from updating the core, no firmware or software updates are required on any of your devices.
So, your PS Audio device doesn’t need an update to receive the b234 changes–they are part of the Core.