Usually incorrect lateral thumb pitch results in blistering or large callouses.  As far as affect on side roll, for a right hander excess right lateral beyond what the thumb hinge calls for can force the customer to rotate earlier and more to be able to get out of the thumb cleanly.  Excess left lateral makes it easier to stay behind the ball.  The proper lateral will allow the customer to either rotate or stay behind (within reason) without hanging in the thumb.  --  JohnP