Rocker was first appeared on the Volant Spatula in 2002, and now features in almost every type of ski from powder to carving. Rocker goes by meany names but the one that I think explains it best is "early rise tip." One of the advantages of rocker is that it helps keep your tips up and on top of the snow while skiing off piste.
With short and narrow skimo skis this can be a challenge, and you end up having to get way in the back seat to get your tips up. This puts you in a bad position to react to the terrain and increases the burn in your legs. With rockered skis you should be able to stay more centred over your skis, save energy, and keeping a strong ski position.
|Dynastar Pierra Menta RC|
"A fairly long, progressive tip-only rocker for improved terrain absorption and impeccable flotation in powder. Ski rotation is facilitated making fore/aft balance easier and reducing muscle fatigue off-piste. The flat tail means you don't lose the tail pressure required for high speed Freeride or off-piste jump landings."
Atomic's rockered race ski is the Ultimate and it weighs in at 700gr. Atomic's literature is very similar: