From what I can see nobody has taken the time to look at the forest as opposed to remaining in the trees. Here's is what I have discovered so far:
There is a list of model numbers Roku claims is compatible with Apple TV+ so make sure your model is on that list (mine is there but ends with an X which doesn't help so I assume it does not matter as you will see reading through this list of item).
Make sure your Roku player has its latest firmware and as well check the TV firmware.
When connected to an effected TV there are some shows which will stream as opposed to displaying the "Video Not Available" message.
If your Roku model supports Apple AirPlay you will find that using it replaces the "Video Not Available" message with "Video format not supported" and I bet this is a clue as to the issue here.
Bet you never tried moving the player to another TV did you? I have five TVs with three being very old Vizio models. I found out the Apple TV+ channel works just fine on the other two TV which are newer!
All all of my TV's using an actual Apple TV device (mine is gen 4) always work fine and as expected.
While you can talk to Apple support their suggestions are similar to what you already see posted and have not worked for me. They stated nothing about what I have discovered and I am in contact with them to report these observations. Apple will escalate this issue to their engineers ONLY after I obtain a Roku support case number (haha).
It is virtually IMPOSSIBLE to talk to anyone in Roku support and likely they will not know about my observation anyway. When I get back to Apple (and their senior support person has given me the credentials to allow this) with my observations maybe they will consider this exception? Their support is usually excellent and part of the reason we pay such high prices for the well designed products.
From my experimentation it is difficult to determine if the issue is with Apple or Roku and the tennis match will likely continue in this fashion unless my senior advisor contact is successful in getting someone in Apple engineering to cooperate. Remember they need subscribers to grow and the Roku player is a much cheaper device solution and it have a potential market segment.
My interim solution will be to move the Roku player to an older TV for which it works fine and then put the Apple TV device on the older TV I want to use.
This situation has shown me some advantages of the Apple TV device as I learn more tricks and tips in use of the simple remote control and better understand navigation techniques. It is very appealing to say the least!!
Good luck to all you having Apple TV+ playback issues with you Roku player and let's hope that some Roku agent reading my post considers making their engineers take a close look at a possible solution.
Stay safe and that includes any life option choices which would make you vulnerable during the pandemic.
Can you please provide more specific information about the issue you are experiencing? Can you please provide us the following information:
-Roku device model, serial number, device ID, and software OS/version (these can all be found in Settings > System > About)
-does this issue occur on a specific channel? if so, what channel and what version/build is the channel (this can be found be selecting the channel on the Home screen and pressing the * button)
-tracker ID when this issue occurs (when you see this issue occur, press the Home button 5 times, followed by the Back button 5 times)
-steps to reproduce the issue you are seeing
With more information we will be able to assist you further.
I gave up trying and simply purchased another Apple TV device and moved the Roku player to a TV where the Apple TV+ channel works correctly. Both my Roku devices behave in this manner on the same TVs. My response is very late because your system for customer support is very poor and I had no interest in monitoring the Roku community postings. As my Roku devices are registered you can easily see their models and software versions. I can by checking my account. I would imagine a Roku employee has access to that same information? I only came back to the community when receiving a first kudu and found your reply. Your system told about the kudu but not your response. How bad is that? Roku get with the program the cheese has moved. This issue is not widespread enough for Roku to bother with I guess.