@milkipedia

Have you tried to change TVs digital audio out format? Automatic, bitstream or passthrough would fit the best.

And how are the Roku audio settings set to?

The TV’s two audio out options are PCM and Dolby Digital.

On the Roku, I change the audio mode from “auto (DD)” to “stereo”, and the audio output format from “auto” to “stereo” (the other option there being DTS).

Let’s see if this helps any.

@milkipedia 

I would try Dolby Digital on the TV and Auto on Roku. Imho DD offers the better quality, but of you prefer pcm stereo try to set Roku on Auto and just the TV to PCM stereo. 

I tried switching the settings around, with no luck.  Next thing I will try is our old Roku 3 instead of the Streaming Stick.

@milkipedia 

How does it work without the Roku just using audio from the tv? If there‘s the same problem I would check the hardware cable connection again trying another HDMI cable. 
And first of all please restart all devices (TV, Sonos and Roku) by unplugging from power source. 

I have done the power cycles.  We don’t have another source connected at the moment, so I’ll have to find something and connect it and try it out.

Replacing the Roku with an old Chromecast seems to help. I will test further.

off to the Roku forums, I guess!

Good luck