This is an absolute joke that you can't remove the remotes completely without doing a factory reset of the device. It always leaves at least one remote paired, in order to get rid of it you have to pair a different remote then you can remove the initial one. But now the second one is locked in. This is completely unacceptable.
The people at Roku are morons, the programmers need to fix this. But don't hold your breath, it won't make them any revenue so it isn't a priority. Stupid things like annoying rows added to the home screen and preset buttons on remotes is all Roku cares about since it gets them ad revenue.