There isn't any. To use the cellphone app to control your roku, the roku and phone have to be set to the same internet network and password. Initially you will need a real roku remote to set up the wifi network on your roku. You can't just use the cellphone app to control the roku, sorry.
Edmund
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee.