I have learned that roll control is by no means necessary, but most people wouldn't willingly do without it.
I would second that.
Admittedly I was only (and unqualified on type) in the RHS when the ailerons locked once for real - in a Hastings , which was a four (piston) engine tail-dragger transport. Fortunately , after an interesting interlude, the problem solved itself on approach . (Suspected icing ).
one is not really in full control of a conventional aircraft unless one has roll control
Absolutely agreed, especially with an aircraft designed from the outset to utilise direct roll control.
To have incorporated this feature it into a vehicle type that had been under evolution for decades , whilst very significant, does not support the claim, believed by so many of U.S. citizens, that the Wright brothers pretty much single handedly invented heavier-then-air flight and designed the "airplane" in the USA, ahead of the rest of the world.