I believe the current device setup process is to enter your email address on the screen. Same process you used before.
Once set up, you won't need to set it up again. If you put it in Guest Mode, when they sign out (or you sign them out) it will revert to your standard setup. You don't even need to be present for that. But of course, you have to be present for the setup.
It may be simple to just set it up at home, then move it to the rental property and put it in Guest Mode.
DBDukes Roku Community Streaming Expert Note: I am not a Roku employee.
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