Do GOO warlocks decide whether to use Entropic Ward before or after the attack roll is made?

Question

The Great Old One warlock patron grants the Entropic Ward feature at 6th level (PHB, p. 110):

When a creature makes an attack roll against you, you can use your reaction to impose disadvantage on that roll. If the attack misses you, your next attack roll against the creature has advantage if you make it before the end of your next turn.

Do you declare the use of Entropic Ward before or after the attack roll is made?

In other words, do you need to declare its use before the roll occurs? Or does it function like the Lucky feat where you can declare its use after the roll but before determining whether it hits?

By the wording, I believe it's before the roll is made, but wanted to clarify.

Answer 1

Before.

In order to impose disadvantage on a roll, the roll has to not already be made.

Lucky is a special case, in that it gives two possible use times - when you make a roll, or after you've made a roll, but before you know the outcome. Other reactions are also given exact time frames: Shield triggers when you are hit by an attack (the roll must be completed to know if you are hit), Parry can be activated "When another creature damages you with a melee attack." Entropic Ward can be used "when a creature makes an attack roll against you," not when a creature has made an attack roll against you, or when you've been hit by an attack.