If the problem is located in the Roku itself, a restart may fix it. If you have sufficient control via the remote you can restart via menu path starting at Roku home screen: Settings..System..System restart.
If you don't have sufficient remote control you can restart by unplugging from the power source then plugging back in after a few seconds.
If a restart doesn't fix it, the problem probably resides in the remote. All I can think of there is to remove the batteries for a few seconds then put them back in. If that doesn't get it, you probably will need to replace the remote.
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