My 2 cents worth there are 3 aircraft that used Spoilers for Roll
controll like they should be. 2 of them were Northrop designs, the P-61
and the C-125, and the other one is the Grumman S-2. They used a mixture
of Spoilers and a small aileron at the tip for roll control. I talked to
a WWII Pilot whoi flew a P-61, He said it was a blast to fly, as long as
you didn't have a nose wheel collapse or land with the gear Up and the
engines running. The rummor was you wound up with a prop blade throw the
cockpit where the pilots legs were.
Bill Higdon
Bill Higdon

Mitsubishi MU-2. A killer, and a special rating to fly it. No
ailerons at all. An old pilot with experience in the type told me that
on an IFR approach in rough air the airplane would lose altitude
rapidly when the pilot tried to keep the wings level. Roll is
controlled by killing lift on the inside wing, and there is no
compensating lift on the other, so the net result is a descent when
the spoilers are busy.
The Helio Courier uses them for low-speed roll control in conjunction
with ailerons.

Dan