Just using a single HomePod mini here, but was unable to stream to it. Roon saw the device, and when audio was sent to it, it appeared to be playing (transport control would change and little moving bars shown) but no audio. Stumbled across a thread that said to change “allow access to everyone on same network” and this worked for me instantly. Now able to stream to HomePod from Roon and actually hear the audio, or move audio to HomePod from another source.
here’s the thread: