Some recent Roku Voice Remotes do not have a pairing button in the battery compartment.
To put these remotes into pairing mode, press and hold both the BACK and HOME buttons near the top of the remote for 5 seconds or more.
Reference: https://support.roku.com/article/360011621473
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.".
Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X