The express comes with an IR remote, which will control all roku that accept IR remotes. To keep them separate you will need to buy two wifi roku remotes, and abandon the iR remotes that came with roku's, both of them. Because if it paired to wifi remote it still can accept IR commands.
Edmund Roku Community Streaming Expert
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You mentioned two different devices: Express and Stick. Those are not the same thing. I'm going to assume they are both Express devices and not Stick devices. If so, what @Tivoburkee is right on target.
If you are able to return them, and get Express 4K+ instead, that would actually be cheaper. The Express 4K+ costs $15 more than the Express. If you bought a Voice Remote, that's $20.
Oh, and the situation would need to be that neither device uses the IR remote, since as you've discovered, the IR remotes will control any standard Roku device. Now, the IR remote will not control a Stick, so if one of them was a Stick, then you wouldn't have the problem. You could keep the IR remote controlling the Express, and the Stick controlled by the WiFi Direct remote that comes with the Stick (similar to the Voice Remote).
DBDukes Roku Community Streaming Expert
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The infrared beams from some remotes are fairly wide so pointing in the general direction can be good enough. And the signals can bounce off walls and ceilings to reach the Roku too, especially in a small room.
Roku Community Streaming Expert I am not a Roku employee, only a user like you. Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X | Streaming Stick 3600
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