The damper is responsible for absorbing the shocks from the road, while the spring is responsible for pushing the wheel back to it's normal riding position and carrying the weight of the car.

Stiffer springs do indeed reduce the body roll, but the weight transfer of the car remains almost the same during braking/accelerating/cornering (although you cannot see it). 

The weight transfer is heavily depending on the center of mass of the car and therefore the ride height. If you reduce the ride height, you have to stiffen the springs to prevent the car from hitting the ground.

If you are going for grip, softer springs are better, especially on rougher surfaces, as the spring will push the tire down more and therefore give you grip where the tire would not even be in contact with the road with stiff springs. Rally cars have much softer springs compared to track cars.

Springs however, have the tendency to swing, which can have awful effects. The damper is there to prevent that and therefore damper, spring and ride height have to be seen together as a unit