Any idea on how I can access them? For example: Showtime and Epix
I don't think you can. I believe that if you paid for them through Roku then they'll only work on a Roku device.
I'm having the same problem. I think if you use the silk browser and download the Roku channel thru the browser it might work. The regular Roku channel app doesn't show my premium bought channels on the Firestick. It does show up on another TV that I'm using Roku Ultra on.
I am also having the same problem, but i am able to watch premium channel through the website and having to stream it using iPhone and iPad to Apple TV. Trying to figure out how to stream to fire stick now. Not sure why it allows you to sign up for premium channels through the app, but not able to watch. This is dumb.
I'm able to watch my paid subscription from Roku on my Firestick using the Silk internet browser. You need to navigate to www.roku.com and sign in with your credentials. It's a little harder to navigate the site with the Firestick remote but it does work. I'm watching a series(Showtime)bought thru the Roku channel right now on the Firestick.