Roller weights are used for fine tuning your scooter to get the most out of what you need from your scooter. 
 Tuning Tips: 
 Light rollers are good for quick acceleration, stop and go riding and hills, but you loose top end speed. Heavy rollers will give you a higher top end speed (long roads) but you will loose low end acceleration. 
 If you�re a heavy person (and/or) if you have a stock motor you will want to lean towards the lighter rollers. If you are a light person (under 140lbs) or you have a big bore you will want heavier rollers