Can the Roku Ultra model: 4802R, play media files such as mp4 stored on a portable USB drive? Articles suggest yes if the files are the right type and the USB drive gets enough power. But after chatting with a Roku support agent they say it can't.
It should, although it is picky about the video format. I have used a USB drive (thumb) to watch videos.
Forgot to add that the Roku Media Player is rather poor, not really supported. There are no 3rd party media players.