All current Roku devices, except the Express non-4K version, are supplied with "Voice Remotes" that control the Roku by radio frequencies (RF) that can go through walls. But each since RF remote will only operate the specific Roku it is paired with, there should be no interference.
The TV control buttons on the Voice Remotes (power, volume, mute) control the TV via direct line of sight infrared (IR) signals as that's what most TVs accept. IR cannot penetrate walls so each remote should only control the TV that's in the same room with it, except for the unlikely chance that the IR signal can bounce from one room to the other through a hallway and still reach the other set. And even then this should not be a problem unless both sets use the same set of IR commands. If you already have these sets in place, and if their individual remotes don't interfere with each other now, this should not be a problem.
The non-4K version of the Express, mentioned above, is supplied with a simple IR remote that controls the Roku only and has no TV-control (power, volume, mute) keys. All Roku units other than actual Roku Streaming Sticks, can be controlled by the same set of IR commands, but except for the ricochet down the hall possibility mentioned above, they will only control Rokus in direct line of sight in the same room as the remote.
