The purpose of the Roku app on your phone is to allow you to connect to and control any actual Roku device(s) attached to the same network as the phone. The phone itself is not a Roku device and so cannot run Roku channel apps. As a courtesy, you CAN view programs on the Roku phone app from The Roku Channel only.
Roku Streaming Stick +, 3810X, Ser YH0059427035, wifi - Samsung UN55ES6100
Roku Streaming Stick, 3600X, Ser 5S56D8240827, wifi - JVC EM37T