An IR roku remote doesn't need pairing it just works, if it doesn't work it's broken.
An universal remote needs to be programmed for the Roku by entering the proper code in to the remote, it won't work directly out of the box.
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.