I started to write it's pretty easy, but it depends on what Roku model numbers you have. If the remote doesn't have a button on the back or inside the battery compartment then it will work with any Roku that isn't a stick and a stick is a device that plugs directly into an HDMI port without the need for an HDMI cable. I'm ignoring RokuTV remotes since you didn't mention RokuTVs.
It gets more complicated with the RF remotes. They all have a pairing button on the back or inside the battery compartment, but some will only work with certain models of Roku devices. You could post the list of Roku model numbers and the list of remote model numbers (inside the battery compartment) and I'm sure someone (@Tivoburkee for example ) could tell you what works with what.
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