Since different Roku models have different features and capabilities you really should report whether you are talking about a Roku TV (with Roku capabilities built in) or a separate Roku device, your model, and if available, model number. This will allow responders to give you targeted responses instead wasting time and effort in giving you general responses that may not apply.
If these are point-anywhere Voice Remotes, they control the Roku device or Roku TV via WiFi-direct and must be paired with the Roku. See this Video from Roku re how to pair point-anywhere remotes: https://www.youtube.com/watch?v=EK3T6eXqPU8
If these aren't Voice Remotes, they are infrared (IR) remotes that can only connect by direct line of sight. IR remotes do not need to be paired and should "just work" as long as the batteries are good. (They will not work with Roku Streaming Stick models which typically are used behind tv sets and so do not even contain IR receivers. For Streaming Sticks you need a Voice Remote as mentioned above.) Be sure there is a clear line of sight between the remote and the front of the Roku or Roku TV. Also note that Roku devices and Roku TVs use different IR command sets so their remotes are not interchangeable.
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