This is going to sound strange, but I don't own a TV, and haven't owned one for 25 years. But we are helping my mother-in-law move into a new apartment, and she has two Roku TVs, one for the living room and one for her bedroom, so I am trying to learn the ropes of setting them up. Unfortunately we are hitting a snag: sometimes when we try to use the remote control to operate the TV in that room, the one in the other room responds instead. Is there a way to pair a remote to a specific TV so that we can control just one TV at a time?
More information, such as model numbers, might help, but in general the remotes that ship with the vast majority of TVs are IR remotes. These send simple codes via infrared light and have no pairing - they simply control anything they are pointed at, as long as it uses the same codes. And since light can reflect, sometimes they will bounce off stuff and not require direct line of sight.
However, I think all Roku TVs can be paired with a Roku RF remote. Those use Wi-Fi and involve an actual pairing process.
The remotes supplied with Roku TVs nearly all control by IR (infrared) signals. All Roku TVs respond to the same set of IR commands, so an IR remote for one set will control any other Roku TV that its signals reach.
IR signals are line-of-site and can't penetrate solid objects, but they can bounce off walls, windows, ceilings, etc. It's not common, but depending on your room configurations, it may be possible for signals from one room to bounce around to reach the tv in another room. You may be able to eliminate this by changing the placement or orientation of the television or seating in one room or the other to eliminate the bounce path. Or if you can shut a door to one room or the other, that will block the signal.
Alternately, you can replace the current IR remotes with Roku Voice Remotes. These connect to the TV via a direct WiFi connection between the Voice Remote and the TV, but each must be "paired" to the TV it is to control and won't control a different set. Roku has three different Voice Remote models and any of them will work with a Roku TV. See this Roku Accessories page: https://www.roku.com/products/accessories
[Note: you DON'T want the $9.99 "Roku TV Remote" -- that's an IR remote like the ones you already have.]