From another Roon user: It was never offered (at all) for networked devices like streamers. So how can it be missing? Use “Device Volume” for your network streamer and enable the volume control feature on the streamer if necessary/supported. Contact Cambridge user support if you need help to setup/configure your Cambridge streamer.
It is not offered for networked devices. Use device volume instead or connect directly to a device that runs Roon (just Roon, Roon Server or Roon Bridge) – no guarantee for the later advice from me though (too many rarely used setup possibilities).
Create a new thread in Feature Suggestions or add your vote to an already existing one if you think that Roon should change in that regard (little chance of getting implemented tough IMHO as there are strong technical and design philosophy reasons that speak against it). Use the forum search to see if there is one already.
Because of latency (time until volume changes are heard, different amount of time passes in grouped zones of differing devices). See also: