Using the remote with different Roku devices
Is there a way that I can use one remote with multiple Roku devices?
Sometimes, depending on the circumstances.
Roku remotes come in two basic flavors: infrared (IR) and WiFi Direct (RF).
All current and recent (last 8 years or so) Roku devices support RF remotes.
All Roku devices except Roku Sticks support IR remotes.
If you're talking about one of the devices being a Stick, then "sometimes" becomes no, since an RF Roku remote can be paired to a single Roku device. However, that Roku device can have multiple RF remotes paired.
If none of the Roku devices are Sticks, then a single IR Roku remote can be used on all the Roku devices. Note that if the Roku devices are close enough so that more than one can see the IR remote at the same time, then both will be affected by the button presses at the same time.
Now, if you were to provide us with some actual information about your setup (including model number) and what you're trying to accomplish, perhaps we can offer suggestions. But to your question as posed, the answer is "sometimes, depending on the circumstances."