There's no way that I know of to get it to forget the setup. You have to go through the procedure under Settings->Remotes & devices->Remotes->[voice remote]->Set up remote for TV control and just choose the wrong brand of TV and lie when it asks if it's working. Some different brands use the same remote codes, so don't be surprised if the first "wrong" brand you choose still works.
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.
