why do you use "roll center ajuster"?

[Ivan141]

Lowering changes the cars geometry, resulting in a moved roll center (the virtual point around which the car rolls in corners). The amount of roll is influenced by the distance between the roll centre and the centre of gravity, the bigger this distance gets (due to lowering), the bigger the amount of roll couple (same force, bigger arm) that influences the car.

To simplify things even further: lowering can increase roll in corners due to the moved roll centre, the spacers move it back to a better position.