Pretty much what slydar said, you need to rebuild the front coilovers with a spacer under the strut insert to in effect raise the insert in the strut and allow more droop. As previously mentioned, i'd aim for about 2-3 inches of droop from static hieght to allow for this countries fine roads (not). For the rear, u need longer shocks, plain and simple. measure what you need and head to a parts place (not supercheap) and find a monroe or gabriel parts book, look thru it till you find something with the apropriate length (comodore, celica, seirra shocks are a good start)
I can put up a few basic pics to explain all this for people if the demand is there, i'll have to draw it up though.
GILLY: what you said about aiming for the middle of the stroke is not a bad idea, if you have shocks with a very short stroke.
The koni dampers I'm going to be ordering soon have a stroke of 153mm front and 143mm rear, so in this case your theory would be pretty good.
However they make dampers that due to there design have anywhere up to 300mm of stroke, now in that case (depending on application) i would be running whatever droop is apropriate and leaving the rest as compression.
HATZO: agreed on the drive car comment but i have no idea what you are talking about with the whole rest of your post, roll steer is bad, plain and simple, as the car rolls into a turn roll steer causes the car to get toe changes (in effect) that cause the car to under/oversteer. The only way that this may be used is if a chassis is over powered for a particular circuit or to solve another problem. For example, say an light sedan (corolla, escort etc) has like, 400kw's, because of the shitty aero traits that this vehicle has it will be a handfull at high speeds, you may want to dial in a little roll understeer to make the car more stable at speed. I can't think of any other reason to have rear roll steer on purpose in a racing sense. Genrally, the problems that roll steer fixes are caused by something completly different that can't be changed (due to class rules for example, ie aero inefficiences).
Unless you are talking about something to do with adjustable rear rollcenters?