I don't know. I've never had the need to do that, so I've never looked up how to do that. I don't think that capability exists, unless it was added in the last update to the Roku OS. Previously, there was no way to disable it.
If you were to press the button, you'd see that it lets you know, in case someone hits it by accident. Try and see.
Do you use any remote features other than the standard arrow and OK button? Would losing the volume and power buttons be a problem? If not, get a universal remote. They are IR, which requires clear line of sight. Roku sells one for $15, but any cheap universal remote would likely work. Just make sure it's compatible with Roku. It'll say so on the box, in all likelihood. Sorry, none of that applies to a Stick.
Or use the Roku mobile app on your phone. You may want to turn Google Assistant or Siri off first, if voice controls are an issue.
Roku Community Streaming Expert
Note: I am not a Roku employee.
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