I couldn´t quite find the answer to this in the rulebook nor the reference guide, so if someone could point me in the right direction, it would be appreciated.

When a card states that you have to spend a specific die, to gain something, does this take place before or after you roll an attack?

EG: "Leading shots".

Thanks.

From what I can tell in RRG, pg. 2 Attack and pg. 9 Modifying Dice, it looks as though dice are spent in the Resolve Attack Effects phase, where it says to resolve any card effects that affect dice, including the Concentrate Fire command / token or spending dice for an effect.

This is more clearly described on LTP pg. 21, Using Upgrade Cards.

Yep, you spend it after the role so it's akin to a target lock in x-wing

Ok, Thank you both for the Quick replies. :-)