it gets very complicated when you find the roll centre depending on the suspension layout - google it and you'll find how the roll centre is determined (see the link above too), and the c of g is located.
but at the end of the day - it's the difference between the c of g and the roll centre that induces the moment to roll the car - and then the springs determine how much it rolls when it does! itr's a combination.
you can even have a c of g BELOW the roll centre, and the car will pitch the OTHER way when cornering! LOL, like a ball on a pendulum round a corner!