I would not have thought that not weighting the tail would cause the roll. So my first question is, are you sure you didn't change anything apart from the tail, such as ballast location, ballast depth etc?
Assuming the answer is no, there is a small argument that does explain the roll. While the tail section has one eye hinge, any buoyancy will just raise the tail section and not affect the rest of the lure. But by adding two hinge eyes, the tail section cannot swing up (as you have constrained the motion to side only), it takes the other sections upwards with it. So as the tail swings outwards, the upward force of the buoyancy applies twist to the whole lure, hence roll.
I am not convinced by this argument, especially if the body is of a dense material, but if the tail section size was significant and the body material was balsa, then it could happen.
Dave