You don't pair simple remotes. They either work when you point them at the device or they don't. A simple remote from a Roku device won't work on a Roku TV. The only simple remote that works with Roku TVs is one from the manufacturer or the Roku simple remote specifically for Roku TVs:
Roku TV Remote | Replacement Remote For Roku TV | Roku
Does this simple Roku remote have tv power button and volume keys on the side of the remote? If it has written on the front Roku tv, what brand is it? A Hisense or Sharp Roku IR simple remote will not work with your RCA Roku tv.