Info for clarity
Roku offers no pay-per-view that I'm aware of. It asks for a credit card number when you create an account, but it is not required.
With the Roku 3 box, you add the Plex channel to your channel list and add the Plex Media Server to your pc. It works flawlessly. Alternatively, RARflix is a turbo charged Plex clone that works with the Plex Media Server. I assume the dongle would work the same.
The Roku remote app for Android delivers way more functionality than the included remote. It allows you to play media stored on your phone, limited voice navigation, allows the use of the phone's keyboard searches and account information entry as opposed to using the arrow rocker to enter one character at a time.