They were wrong as you found out, no roku remote without a tv power key will work on any Roku tv, those are stand alone roku's remotes for such models as the express, premiere, and ultra. Roku doesn't sell IR Roku tv remotes that you would have to get from tv manufacturer. Roku does sell Wifi Roku tv remotes, which do have pairing button in the battery compartment. It won't work on your tv straight away, it has to be paired first.
Please contact your TV's manufacturer directly to report this issue and request additional support. Each Roku TV manufacturer provides direct support and warranty services for their products running the Roku OS.