All TVs have a power button, but it's often hard to find. It's usually located near/behind the manufacturer's logo or near the IR sensor for the remote if it's not on the back.
You have to pair the Voice Remote before it will work with the TV. If there's a button on the back or inside the battery compartment, press and hold it until the light starts flashing. If there's not a button, press and hold both of the top buttons (Back and Home) until the light starts flashing. Turn on the TV with the power button or try unplugging the power cord for a few seconds and then plug it back in. Don't press any buttons on the remote until the TV and remote connect.
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.