what's funny is when i restart the roku the picture returns.
Perhaps the Roku device has either lost its HDMI handshake with the TV or has gone to sleep/low power mode when this occurs.
See if any of the below saves you from a restart.
1. Try pressing the Home button a couple of times to wake the device. (should only take one press, but a couple wont hurt anything).
2. Using the TV remote (not Roku remote) try switching inputs (i.e. select HDMI2, then back to HDMI 1). Basically, switch to another input, then back to the Roku input.
3. Try disabling Auto Power Savings if available on your device. Go to Settings/System/Power/Auto Power Savings/20-min [Disable]
4. Try powering your device from the wall if currently using your TV USB port for power.
The restarting of the Roku device is likely re-establishing the HDMI handshake between the device and the TV.