yes, generally if your skis have a good amount of rocker, it's not a bad idea to go a little longer. rocker skis have less sidecut (part of the edge that touches/grips the snow) due to their shape, and thus you need longer rocker skis to match the sidecut of regular camber skis. all of this is especially important if you're worried about holding a good edge/carving on hard pack. or, if these are for powder, they should generally be bought longer for flotation anyway.
but i'm not an expert or anything.