What Rowen said, plus this.
Rockered park skis are the current wave of the future, so it's a two part question.
#1 What problems/solutions are we trying to recognize/solve in park skis in general, and #2 How do rockered skis fit into these problems/solutions?
#1. Park skis have been, by and large, soft, narrow, and regularly cambered. I see all of these as problems. Soft skis work for buttery creativity, but they are far more of an issue on jumps over thirty feet unless you can land perfectly centered at all times. Narrow is a similar problem, because the skinny landing platforms aren't as stable as their wider brethren. Hence the growth of park skis by about 5-10mm in the waist over the past few years. And then the camber issue, which
#2. has switched for a number of reasons, all related to these other problems. Rockered skis don't need to be soft to still be butterable, so you can have a ski that allows you to slide around but won't wash out on large kickers.
Rocker gives the ski the upturned portion that the tip has traditionally constituted. You can dispense with the length of ski needed for that traditional down camber and upturn to tip, which yields less material length and less swing weight for the same length of ski.
Many of the guys leading jibbing right now are using way more than 90 degrees to the rail. This means that the catch points in a ski's sidecut are increasingly important to consider when designing a jib ski. Regular camber, when paired with regular sidecut, puts the widest section of the ski at the contact points of the camber. If a skier is doing a contact spin on a rail, this intersection can be a snag point. Rocker, however, allows these catch points to be elevated above the level plane of the base, and so more creativity can be achieved with less hassle.
With it's original use in soft materials, rocker provides a bit of float that wouldn't otherwise be there on a park ski. Slushy landings and ruts don't bother me with rocker on my park skis.
Overall, rocker with a park ski is just like rocker on a pow ski--something new that you either like or don't. My biggest suggestion is to try it out, and see how you like it.
"I dont know what we're talking about, but I'm sure someone will find a way to hate on it." - Ginko