Rotation is dependent upon flexibility, posture (a curved spine, or “C” shape posture over the ball, won’t turn as well), and good footwork. If you’ve lost rotation (I have, due to aging), and you’re working on gaining some back, GREAT! But, a word of caution: many times, to increase turn, a player will lose control of their weight on their swing side (right, for righties), allowing it to move to the outside of that swing side foot(right, for righties again), instead of loading onto the inside. With the weight on the outside of the that foot, it is almost impossible to start the downswing with the legs, arms following. In fact, I find it to be the leading cause of “coming over the top”.
One other word of caution: Don’t work on this during a round. Changing where your backswing ends necessitates a change in timing, but when you don’t have an accurate sense of where you are at the top, or if it’s a little different each time, instinctive timing suffers and it’s bound to be a long day on the course.