Thanks for the note.
Try removing the YouTube channel from the Roku home screen by navigating to the channel tile, pressing the * key and choosing 'Remove channel'. Then, restart your Roku device. Once it loads up again, add the YouTube channel back once more from 'Streaming channels' and try your content again. If you're still running into the issue, you might try connecting your device to a different HDMI port on the TV to test if the same issue occurs. If so, you'll want to contact YouTube support to report the issue within their channel, and request additional assistance. You can reach them directly here: www.twitter.com/teamyoutube
If you need more help, feel free to PM me and I'll see how else we may be able to assist you.
Roku Community Manager