I hadn't intended to include this here, as I thought it available at many other sites. I found, however, that a more general solution might be of help to some.
This program determines the roll center location for linkages commonly found in an automotive independent suspension. You'll be asked for the "x,y" locations of the right front and left front tire patches and the locations for the pivot points for the links. The origin can be anywhere, but I find it most convenient to consider myself looking forward from the rear of the car and the left front tire patch is the origin (x=0; y=0). And, "x" and "y" could be orthogonal axes pointing in any direction, but most people would probably have the "x" axis horizontal with positive toward the right front tire patch. If you're used to the SAE coordinate system, my "x" is in the direction of the "y" SAE coordinate and my "y" would normally be positive to the negative "z" SAE coordinate. The program checks for parallel links and makes the necessary corrections.