You could also use the CC sphere to simulate this but its a little tricky because it's not really 3D.
But just for a 2D ball , you can put an expression on the ball - you keyframe the rotation and then apply the math of: distanceTravelled = 2*Pie*R*rotationAngle/360
I couldn't figure out how to post the symbol for Pie
R is the radius
This way the balls "sticks" to the ground as it rolls and doesn't spin at the wong rate.