Roku tv's use two very old tv code sets, the majority use the Admiral code which include the Onn brand. The Hisense & Sharp use the LG code, original the Goldstar code set. Some Hisense roku tv's respond to both code sets. The remote you have is the wrong code set. sorry.
You can purchase the roku wifi voice remote from walmart or best buy, it won't work out of the box it will have to be paired with the Onn roku tv. But they work with ALL brands and models of roku tv. Its $19.88 at walmart and $29.99 at best buy. You can find the One-For-All urc-7935 streamer universal remote that is the remote on the right in my photo above in walmart for $25, it works great with roku tv's. They go for $10 on ebay.
I bought a replacement remote it said Roku but there is no pairing button it still works great also you can download an app Remote free your phone becomes the remote works great
Roku TV WiFi remotes will pair to such stick models as 3600, 3800, and 3810. It will not work with the purple 3500 stick. But Roku tv WiFi makes terrible stick remote reason is the tv power and volume commands are useless to any other tv but Roku TV's.
And the remote on the right won't work with Roku sticks at all, being IR only.
my REMOTE ia a ROKU remote purchased at WALMART about 4-6 months ago at Walmart in Red Bluff Ca dont know model # but it is NOT a stick it is the middle grade and it DOES NOT HAVE A PAIRING this is my THIRD device so I know what you are asking about a PAIRING button
Remotes without pairing keys are IR only remotes. A Roku Stick can absolutely NOT be controlled by an IR remote, only Wifi Roku remotes.