I am having issues with the Roku sound bar not playing movies on Netflix. I had first thought it was a Netflix issue. But played the same films on my iPhone and they work fine. I also have some of the same issues on YouTube as well as AppleAir. I have a Roku TV. Have had no issues with it. Plus when I hit the volume it only goes to like 25 to 32 and the numbers vanish.
Try removing the channel(s) from the Roku home screen by navigating to the channel tile, pressing the * key on your remote and choosing 'Remove channel'. Then restart your device from Settings>System>System restart. Once your player starts up again, add the channel(s) back once more.
Does this clear up the issue you are seeing? Please keep us posted what you find out.