Rock Crush states:
R: After you play a block, any attack you play as a Reversal to that block gets +X damage. X equals the difference between the difficulty of your attack played as a Reversal and the block modifier of the card you played to block.
Since Rock Crush's activation point is "after you play a block" can you play the Reversal and then react with Rock Crush to boost it? Or do you have to Rock Crush first then Reversal?