This exercise is best performed with a weighted squeeze ball designed for developing grip strength. The balls are usually rubber and filled with granular lead or something similar. You can substitute another object that fits in your hand such as a can of soup. Hold the ball (or object) firmly, and rotate your wrist in complete circles. After performing the prescribed number of repetitions, rotate your wrist in the opposite direction.
Another alternative is to use the grip clamps. It's best advised these be used in combination with the roll exercise and not as an alternative. These clamps offer various levels of resistance so be sure to get ones suitable to your strength level. The Tennis Ball Squeeze is a good alternative to grip clamps.
