Theres only one (L and R) audio out from the Roku.
Sounds like the anlog audio out is going to the one receiver. You could TRY running the digital audio out to the other receiver. Otherwise, I think you'd need an audio analog distribution amp to get the audio from the Roku to both amps simultaneously.
Alternatively, I suppose if the wanted to spend bucks you could either:
a) get another Photobridge
b) get a new multi-zone amp and put speakers at both locations, programming the Crestron to set the amp to the proper output zone for the viewing location.