Factory reset is accessed via Settings > System > Advanced system settings > Factory reset.
Alternative is, while set is powered up, to press and hold the reset button (may need to use a paperclip to access though a pinhole) for a MINIMUM of 30 seconds, Don't release early no matter what you see on the screen.
Either way, when the Roku boots back up, its memory will have been cleared and you'll then have to set it up again as though it were a new unit right out of the box.
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