Welcome to the Roku Community and thanks for post regarding your audio issue on the Roku TV.
In order for us to better understand the issue it's important that we rule out variables see what is the root cause.
If you disconnect the Vizio soundbar, do you experience the same issue occur with both Auto and Passthrough? Likewise if you disconnect the Apple TV but connect the Vizio soundbar?
Please keep us posted what you find out with trying these steps so we can better understand what you are experiencing. We look forward to hearing back with your response.
Roku Community Moderator