I believe you are mixing terms here. You don't/can't "pair" your phone to a Roku. Screen sharing is not pairing. I don't have an Android phone, but when I did back in 2017 I had to install an app on the phone to make it visible for screen sharing on my Roku. Perhaps the newer models no longer require that app, but in any case the phone has to have the function enabled to screen share the phone to the Roku. I can screen share my iPhone and my Windows laptop without a problem.
Make sure the Roku has Screen Mirroring Mode enabled in the Settings/System menu.
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, just another user.