When seeking help it's always a good idea to report your Roku model, model number, and Roku software version as shown via Settings > System > About. Different models have different features and capabilities, and some things depend on the Roku version you are running. If we have this information to start with, you can get targeted suggestions more quickly.
You haven't really given us much to go on.
When do you have the problem? On Roku home screen? All channels or just particular channel? Channel home page and menus or just when viewing a program? Any other info you can provide that might help us understand the situation?
Have you tried just restarting your Roku? Depending on your Roku model and Roku version number you'll find the System restart option under either Settings > System or Settings > System > Power. (If this is a Roku TV, just turning it off and on doesn't give you a complete restart.). You can also restart by pulling the power plug to the device for a minute or so then plugging it back in.
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. If this post solves your problem please help others find this answer by clicking "Accept as Solution.".
Streaming Stick 4K+ 3821 | Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X