I have a Tablo connected to my wired network and use a Roku Ultra to access the Tablo. I play audio through a Yamaha A/V receiver.
I tried using surround sound when Roku first released it but ended up turning it off due to issues with live events, particularly shows that have voiceover. I tried surround sound again tonight with the Olympics closing ceremony but still experience the same symptoms.
What happens is the voice over (announcers) is comparatively very loud versus the music and other sounds from the actual event.
I have seen this with other live shows such as Dancing with the Stars and sporting events.
Commercials come through just fine.