You will need a Roku for each TV. Some models come with a voice remote and some don’t. Even if it comes with a voice remote you aren’t forced to press the button. XFinity has a voice remote but your not forced to press the button either. The voice button is there for convenience. Note that a Roku does not have numbers on the remote
Each TV that is to receive Roku content must have a Roku device attached.
Most devices come with a Voice Remote. That's the name of the remote, and describes an optional feature. I have Voice Remotes on all my Roku devices, and have never used the voice feature. It's optional. I always press the buttons.
The answers to those questions apply to all the Big Four streaming device platforms, and likely won't impact a decision to choose Roku over any of the other platforms.
DBDukes Roku Community Streaming Expert Note: I am not a Roku employee.
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