Remote controlling multiple rokus

The simple infrared (IR) remotes for Roku devices (no power, volume, or mute buttons) all use the same IR control set and will control any and all non-Streaming Stick Roku devices they are pointed at.

The remotes supplied with Roku TVs use a different set of IR commands and control Roku TVs instead of Roku devices.

Streaming Stick Rokus are normally used behing the TV where IR can't reach so they don't even have IR receivers and can't be controlled by IR remotes.  Instead they are supplied with remotes that control via radio frequencies (RF) that can pass through TVs and walls.  Each RF remote must be linked to the Roku unit it is to control and will control only that unit.

Roku also makes and sells RF remotes that can be paired with and used with all current Roku devices, most older Roku devices, and Roku TVs.  They are the Voice Remote (~$20) and Voice Romote Pro (~$30), available from Roku and many retailers.  With a Voice Remote model paired to each Roku you can control each Roku separately.

Another option is to use the free iOS or Android Roku app on a phone or tablet to control your Rokus.  It will "see" all the Rokus, both devices and TVs, on your local network and allow you select which one you want to control at a time.