Apple TV app not working on Roku (June 2023)
Some of the answers given in other threads are for older Roku devices or software versions. If you get a Message saying "Video Unavailable" and "There is a problem loading this video, If this continues, please check your internet connection." Then you actually need to change the Audio Mode to Stereo. Don't ask me why but after I did this it started working fine.
Here is a screenshot of what the menu looks like. You get here by going to the Roku box's settings page, then Audio, then Audio Mode and this should be set to Stereo as shown here.