Yes, this is a known shortcoming of the Apple TV app, that from what I’ve read is not likely to be fixed.
It should not be a problem with Roku, however, so you should concentrate on troubleshooting that. Contact @TabloTV for help if necessary.
There is a separate, outstanding problem with Roku that can affect either playback or sound. See here: https://community.tablotv.com/t/update-on-4th-generation-tablo-compatibility-with-roku-os-14
Had TabloTV gen 2 about a month.
To avoid confusion here, be aware it’s called “4th gen” 