Are you required to roll all attack dice?

[Drail14me]

When attacking, are you required to roll all attack dice in the weapons attack pool? For example, when Operative Darth Vader is in melee and attacking with his lightsaber, does he have to roll all five red dice or may he choose to roll fewer dice?

[TalkPolite]

Hey there, 

You must use all the dice for each weapon you attack with. 
 

TP