apple tv purchases not available on Roku devices

Perhaps the extra features (trailers, etc.) somehow confuse the Roku device or the Apple servers.

iTunes Extras are not available on third party streaming devices. Just the main feature would be available there.

If you can't view your iTunes Extras - Apple Support

Although that wouldn’t result in a "Video Not Available" message, I think.

You're only able to view iTunes purchases and other streamed content on your Roku device.

Watch movies, TV shows, and live content in the Apple TV app

My Apple TV+ subscription does not work on my Roku device. Keeps Showing video not available