I have a 32' Itasca F450 Ford class C motor home with the 1,000 lb Sumosprings installed in the front and still get a fair amount of body roll. I talked with a vendor and he said to put on the 1,500 l...
Will auxiliary springs with stiffer spring rate reduce roll/sway? YES.
BUT, (yes, big BUT) they will also stiffen the ride/make it ride harsher.
As already posted, if roll/sway is the problem, not bottoming out, then stiffer sway bar bushings and/or larger diameter sway bar will reduce roll/sway without materially stiffening the ride.