Can’t stream AppleTV on TV. I have Roku.

Check with ROKU support. They have had many issues with some resolved by a software update. Other users have reported that deleting the Apple TV app and reinstalling solved the problem.

https://support.roku.com

And here are their community pages:

https://community.roku.com/t5/forums/searchpage/tab/message?advanced=false&allow_punctuation=false&q=apple%20tv

Have you tried a Roku restart?

Else:

Another user (mygreensocks) suggested this procedure from Roku Support staff, which reportedly helped several users.

1. Remove the Apple TV app,
2. Shut off and unplug the TV (or streaming device),
3. Wait 30 seconds,
4. Plug the TV (or streaming device) back in,
5. Reload the Apple TV app.

Else try the Network Connection Reset, as mentioned by user Jarieta.

1. Roku: Home﹥Settings﹥System﹥Advanced System Settings﹥Network Connection Reset

If the issue persists after that, then please contact the Apple Support staff for further assistance.