Can you please provide us with more specific information about the issue you are experiencing? Is the issue you are experiencing only happen on a specific channel or on all channels? Have you tried using another HDMI cable to connect your Roku device?
As a first step, could you try to restart your device from Settings>System>System restart? (For Roku TV Settings>System>Power>System restart)
Please keep us posted and we'll continue assisting you from there!