I am unable also to open the apple tv app on roku. I just spent an hour on the phone with Apple, and went thru all the steps they suggested, and it still doesn't work. It seems that the apple app is trying to open, it goes to a dark screen, and for a tenth of a second, I can see the apple logo, but then the screen goes back to the app page.
I have uninstalled the apple app, restarted roku, and then, reinstalled the apple app, no luck. I have changed the audio to Doby Plus with no luck. I am beyond frustrated. The apple rep told me to contact Roku, so here I am.