@Dcrom13
I would login to my account at https://www.roku.com/ and cancel any subscriptions I currently have for the RokuTV. Then "unlink" the RokuTV from your account (located at bottom of the main account page). This should at least force the "new owner" to have to factory reset the RokuTV in order to get it working again and not have access to your subscriptions.
If you have subscriptions you need for other Roku devices, then the "unlinking" procedure should be enough to at least disable the RokuTV's access to them.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102