@ampre-
When you turn your TV on, if it comes up still showing the HDMI port to which your Roku is attached, see if switching the TV to a different input and back to force the TV and Roku to do a new HDMI "handshake" makes any difference.
If that helps, try getting in the habit of switching the TV to a different input before turning it off.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
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Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X