I can't watch any series or movies from Rokutv app on my Android cellphone or tablet. I'm in US.
The Roku app's primary intended function is that of a remote control for the Roku. The only program content you can view on a mobile device via the Roku app is from Roku's own The Roku Channel for which they own the distribution rights.
Additional channel subscriptions you may have through Roku that you view through The Roku Channel generally only grant Roku the right to stream to Roku devices, not to mobile devices, and so can't be viewed through the Roku app.