Also A54

In some cases, you must resolve them sequentially, not all at once. For example, an area power that slides each target it hits -- you have to know where one creature ends up before moving another creature, because the first one might block (or free up) a lane of travel for the second and third.

Since I've seen no hint that some powers are not resolved sequentially, I've always played that they all are, any time it matters. Roll one, adjudicate, roll another, adjudicate.