The Roku app on mobile devices is primarily an alternate remote control for Roku devices and TVs.
Streaming rights for televisions, desktop computers, streaming devices, and mobile devices are all licensed separately. You can view Roku's own The Roku Channel via their mobile app, but not other channels for which Roku does not have the right to stream to mobile devices.
Roku Streaming Stick +, 3810X, Ser YH0059427035, wifi - Samsung UN55ES6100
Roku Streaming Stick, 3600X, Ser 5S56D8240827, wifi - JVC EM37T