Thanks for posting regarding our inquiry.
The appropriate Roku team is trying to understand the behavior and steps to reproduce the issue. For clarification, when you are using the sleep timer on the TV, are you:
1) playing content through the Roku Streambar - such as viewing Netflix or another channel on the Roku device
or 2) are you watching something directly through the TV, such as OTA or using another input such as playing a movie on a DVD player - and simply using the Roku Streambar for enhanced audio?
Once we have this information, we will be able to pass it along to the appropriate team to look into further. Please keep us posted.
Roku Community Moderator