Remove the batteries from the Roku remote
Unplug the Roku device from power
Wait 10 seconds
Plug the Roku device back in
Reinsert the batteries into the remote
If it is a voice remote, press and hold the pairing button for 5 seconds
Wait for the pairing light to flash
Re-pair the remote to the Roku device
If needed, replace the batteries with fresh ones
If needed, restart the Roku device and try pairing again