I use Roku to typically watch Hulu and Plex. I plug the Roku by HDMI to my Onkyo AVR. I have noticed that the sound experience is not that great and mostly focused on the front speakers. Checking the AVR, I see that the Roku device is being received as a 2 channel PCM stream. When I plug other devices into the same port and play the same video, my AVR sees them as a multi-channel PCM stream or a 5 channel PCM stream.
I have gone to the Roku settings and changed it to both auto and Dolby Digital with no change.