Sometimes it is necessary to roll quite a few dice to resolve shooting - whole handfuls at once in fact! This doesn't take as long as you might imagine because all the dice are rolled together. The most practical way of going about this is to take as many dice as you have troops shooting and roll them all at once. So, if you're shooting with ten Archers, roll ten dice. Then pick out any dice that score a hit and re-roll them to wound. So, from ten dice rolled, four might typically score hits. These are re-rolled and may score 2 wounds, for example.
Dice that score wounds are picked out and handed over to your opponent to take his saving throws with. This same system applies when working out close combat.