Depending on what car you have the CoG will be roughly between 13mm and 17mm over the bottom side of the chassis, this is without the bodyshell taken into account, which has a big influence on the CoG since it's about 7-8% of the mass of the car with a very high CoG.
The Roll centre being a virtual point which position changes at every moment it doesn't matter wether it is "in" the car or not, what matters is if it's over or under the CoG and what the distance is. Also, when your car rolls the Roll Centre shifts to the side (because the arms aren't angled the same anymore), how much it shifts is relevant as to what the load distribution between the left and right tyre is going to be.
Now for the fun part, there is no way you can really know what the car is going to do while cornering, other than to design it with a CAD software and run a very complex dynamics calculation. Simply because there is no other way of knowing the exact location of the centre of gravity (whose location in space means as much as its vertical location). Not to mention the even funnier part of knowing what's happening in the shocks !
But the good part is, all the work's been done for you ! Just trust the manufacturer's development and work out how your car behaves when you raise or lower it, just don't bother about its exact position as it don't really matters to you.