Right now this is as I understand it: A camber link that is parallel to the arm (raising the inner ballstud) will make the roll center lower. Making the link angled down towards the inside of the car will raise the roll center.
Raising the hinge pin above the chassis actually lowers the RC and vise versa, although most people refer to raising the hinge pin as raising the rear roll center. I've always found raising the hinge pin will make that end of the car flatter though.
Check this out though
http://home.tiscali.be/be067749/58/c2/index.htm