Thanks for the post.
Have you tried using another HDMI port to connect your Roku device as well as switching out the HDMI cable? For troubleshooting purposes, have you tried connecting that Roku device to another TV to see if the experiencing the same issue. As a last resort we would recommend unplugging the power of the Roku device for 10-15 minutes then powering it back on to see if the issue is still occurring.
Please keep us posted what you find out and we will be able to assist you further.
Roku Community Moderator