The AppleTV app connects to your iTunes account and plays items from the cloud, not your local computer or iDevice. Mine is linked to Movies Anywhere, so all my digital media as available via Apple TV, MA, Vudu, Google Movies and Prime video. However, my 4K titles are not available in 4k from all of them. I have to jump around to find a 4K version sometimes, although I think MA usually has them all in 4K now.So is there an iTunes app on the Roku Ultra? Seems the best choice for 4K video.