ok, I'll take a stab. it seems to me what you want to do is first figure out the direction the ball needs to roll in the X/Z plane. direction = atan2(z,x), something like that. Then, rotate the ball around the Y axis (yes I mean Y axis) by this amount so that Z is pointing along the direction of travel. Then, rotate around the X axis an amount based on how far it should move, which you can figure out based on the ratio of the distance of travel in X/Z over the circumference of the sphere * 360.0. There would be no rotation around the Z axis. Be sure to convert radians and degrees properly.