On a more or less normal sailplane design the tail surfaces are far too short in span to be able to control the roll at all let alone effectively. There just is too little leverage to be able to control that long span of the wings.

Even on a regular sport power model they are not spaced out far enough to work decently. A fellow with a relatively low aspect ratio bipe wanted to put all this work into just the two tail surfaces and used a larger stab and elevators as ailevators. Apparaently it didn't work worth a hoot and he dumped it trying to make it fly This was a 30 inch span bip with darn near a 14 inch span elevator if that is any indication.

To even stand a chance of being effective your stabilators would need to have a span of at least about 50% of the wing's span. And that would be a pretty darn funny looking model.