The rocker does not do anything for the stiffness or strength in the laminate. It might pre-stress some of the layers if the layers are cut to fit a straight plank and then the plank is bend into shape in a press after the layup and impregnating is finished.
The stiffness is closely related to the height of the sandwich construction since the height of the beam is elevated to the power of three. The stiffness is of course based also a product of how stiff the materials you are using are, however, since very low Vf's are reached with hand layup the most dominant factor is height.
Adding a shape to the surface of the laminate can give you added stiffness, think of a corrugated plate vs. just a sheet of the same material and thickness.
The strength is related to the orignal strength of the two components and the amount of layers / cross sectional area.
So if I was building a TT with some medium density closed cell foam, I would add that to the area between the pads and then taper that down towards the edges with a long slope towards the tips. I think torsional stiffness is most important so a +-45 degree layup will probably promote easy riding characteristics. That will give you most flex along the length of the board and minimize the twist.
The outline is very important for the riding characteristics as well so look at some of the good freestyle boards of today and use that as the base. Measuring and matching the flex characteristics of a production board will be very hard, it is most likely faster to just try different layups and core materials.