So...of course...as soon as I post the question, I find what I think is the answer here:
https://developer.roku.com/en-gb/docs/developer-program/authentication/on-device-authentication.mdIf I'm reading this correctly, this is the new way developers must register and validate via the rendezvous (just discovered that was the term I had been missing) login authentication. So to confirm from someone who knows this better than me:
1. Validate they have a valid roku account and logs in accordingly.
2. Send the email associated with roku to our API which will make sure they have a valid membership
Sooooooooo then is it possible for us to create a "My Custom Workout Videos" section and then when they click on it...have it go to our API and retrieve the appropriate JSON which may have one or many videos for them to click on and watch?