There is a lot of confusion over the role of the wrists through the impact zone in golf. There are two very different aspects to consider here. The first is the rolling of the wrists. This is the turning of the right wrist over the left to square the club face to the ball through impact. i have addressed this issue in the Use a Strong Grip tip where I advocate the use of a strong grip to lessen the amount of wrist roll necessary. please read this if you are interested.
The second aspect of the role of the wrists through impact is the correct forward backward bend of each wrist through the impact zone. This what will be discussed in this post.
As you come into the impact zone (as a right hander) your right wrist should be slightly bent backwards and should remain there through impact. Amateurs tend to feel the need to straighten their right wrist and hit the ball with their right hand by flipping the wrist. They are probably not even be aware they are doing this.
Any effort to influence the contact or ball flight in this way will be totally unpredictable and certainly detrimental.
It is essential to regard the hands as a unit when playing golf. Their role is largely passive through the impact zone. The power comes from an efficient swing and swing mechanics, not from manipulating the wrists through impact.
Your left wrist should be flat and your right bent back through impact which will necessitate your hands being well ahead of the ball through impact. All of these things are essential for correct club/ball contact.
Late release or uncocking of the wrists in the downswing will greatly aid in achieving the wrist positions outlined here. A helpful thought is to delay the ball contact as much as possible. Build the idea and feeling that everything is lagging behind your hands in the downswing. Believe me, the club head will catch up no matter what you do and the later this happens the better. Try it and see.