This is what a snowboarder friend told me about rockered decks in parks. He said fundamentally they're not as good as a normal camber deck, but the allure for rockered decks, for snowboarding atleast, is that they are super "skatey" feeling.
So his opinion was that rockers in the park don't help or make anything easier, in fact they may make it a little bit harder, but apparently it's just a different way of riding that is fun.