I agree with Snipafist, I think the intent is probably to replace the dice before the roll, but can understand how it could go either way. If he was after the roll, I think he might be just a skosh too good with additional reroll effects.
If it's before the roll, though, he's a skosh too poor for his points. His ability is certainly powerful, but his requirement for squadrons to be in place is a somewhat significant limitation. I'm a bit bias, though, because I really really want to pair him with naked Nebs.
Edited by Truthiness