Try disabling the Power Savings Feature of your Roku device in the settings.
Settings/System/Power/Auto Power Savings/20-min inactivity [uncheck to Disable]
The power savings feature seems to cause some HDMI handshake issues on some setups. Normally, just pressing the Home button will wake the Roku from both sleep and this power savings mode. However, some have found it necessary to disable completely.
If you aren't already, remember to press the Home button when you are finished streaming before powering down the TV. If you aren't doing this, then the Roku will continue streaming and if enabled, this power saving feature will kick in, requiring you to press the Home button to wake up the device. Some Roku users mistakenly think the Power button is for their Roku device, but it is only for TV control (has no effect on the Roku device).
Just mentioning the Power button confusion above in case you are new to Roku.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660x, Premiere+ 3921, Express 4k+ 3941