Here's where things get a little complicated.
Roku TVs usually come with a version of the Simple Remote, but configured for Roku TV. They are IR remotes, and don't require pairing.
The standard Roku Simple Remote you can buy online or in a store (Walmart, Best Buy, etc.) is not compatible with Roku TV devices.
The higher end Roku devices, as well as the sticks, use an RF (WiFi Direct) remote, available as the Voice Remote, the Enhanced Voice Remote, and the Voice Remote Pro. They come with the higher end devices: the Ultra, Streaming Stick line, etc. Those won't work with many older (over around 4 years) entry level devices, but will work with sticks and most current boxes.
The WiFi Direct remotes will work with Roku TV devices. You have to pair them. There's a button under the battery compartment of the remote. Roku has a page about it.
One other thing: Roku had one other remote several years back. The Roku 2 XS came with a Bluetooth remote. It's the only device that came with that remote, and Roku went with the WiFi Direct remotes when the Roku 2 XS device was discontinued, replaced by the Roku 3. If your friend had an older Roku 2 XS and gave you that remote, there's no chance of it working.
If the steps listed on the Roku Remote page I listed, or other suggestions others offer, don't work, the only solution is to get a Voice Remote ($20) and pair it to your Roku TV. I'd suggest buying one locally (Walmart, Best Buy, Target, etc.) so you can return it if it ends up being the Roku TV that's the problem instead of the remote.
Roku Community Streaming Expert
Note: I am not a Roku employee.
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