Express 4k + auto power off
This Support Article https://support.roku.com/article/6306527767575 describes what the Auto-Power Savings feature is and how to disable. (also described by Strega2 ).
Basically, if the Roku detects an inactive Roku state (no active streaming or remote presses), it is supposed to put the Roku device into a sleep state and attempt to turn off the TV.
None of my Roku devices are able to power off my TVs though, so may just be manufacturer or model dependent. You should also verify that your HDMI CEC is Enabled in your TV settings (using your TV remote, not the Roku remote) to help the Roku device communicate with your TV functions if you want to see if this feature works for you when Enabled.
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As mentioned by Strega2 also, I don't think having the Power Savings feature Enabled is worth some of the issues it potentially causes with HDMI/HDCP errors.
Just make sure to press the Home button after you are finished your streaming session (to return to Home Screen) and then press Power to turn off the TV. The Roku device should fall asleep after a few minutes.
