Powered off and it's still sounds like it's running
I need help, is this a hazard or is this fixable????
Generally, for RokuTV issues like this, you will need to contact the manufacturer to address.
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Have you tried unplugging it for a few minutes to see if that helps. Generally with newer TVs, there are very few things that are "running". Very few have fans anymore as they are mainly LED and electronic boards inside. Any noises now are likely some interference sounds/audio speaker issues.
If you are concerned with any hazards, unplug the unit when you are finished watching it and check with the manufacturer in the above link.