Roku voice remote pro unpair from TV power and volume settings.

Go back into the remote configuration and set it up again.   Set it to some tv other than yours by lying to it when it asks to confirm whether you can still hear the audio.

Roku menu path:
"Settings -> Remotes & devices > Remotes"
At this point if your remote has already been setup for the tv but you need to reset it, arrow down to select your Remote (in use).
Now select "Set up remote for TV control" .. And follow the prompts