A head over heel rolling putt means that the ball rolls around its horizontal axis. This results in the top (head) of the ball rolling over the bottom (heel).
It is really easy to see whether your putts roll head over heel if you draw a line around the equator of the golf ball. Set the ball up on the green so that this line aims along the target line. Hit your putt and if the ball rolls so that the line remains vertical, then your putt is rolling head over heel.
When you hit your putt, if the line on the ball does not remain vertical and it topples over as the ball rolls, this indicates that you are hitting the ball and imparting tilted axis spin on the putt. Tilted axis spin means the ball is not rotating around its horizontal axis. This happens when the ball is struck by the putter head and the putter face is aiming in a different direction to where the putter head is travelling. The divergence between the face aim and head direction of travel, results in the ball spinning off its horizontal axis and as a result of this, the ball will roll off the intended line of travel, rather than follow it.
To create a head over heel rolling putt, the putter face must be aiming in the direction where the putter head is travelling. If this happens as you strike the putt, the ball will roll head over heel and remain on the target as it moves. Being able to putt with a head over heel roll will allow you to hole more putts as you will hit the ball more accurately along the target line.
In order to create this head over heel roll, ensure that you initially set up aligning the putter face down the target line and then setting your feet up parallel to the target line. Set your feet shoulder width apart and position the ball in the middle of your feet. As you take your posture up, ensure that your eyes are positioned over the ball, or just inside the ball position and then allow your arms to hang freely under your shoulders. Place your hands on the putter whilst keeping your arms extended and freely hanging your shoulders.
This set up position will allow you to swing the putter like a pendulum from your shoulders. You will be able to make a stroke that moves straight back along the target line and then straight through the ball along the target line into the follow through. As you make this action, ensure that the shaft of the putter remains vertical, initially in your set up position, but specifically through impact. If you move the putter through impact with the shaft in a vertical position like this, then you will present the putter face back to the ball with the correct amount of loft on it. With this action and the putter head travelling along the target line, if you ensure that the putter face aims down the target line as you strike the ball, the putt will roll head over heel and hold the target line.
To help you maintain the correct vertical shaft angle through impact, work on the following drill to maintain the angle that you set in your right wrist at address, through impact. Set up and hold the putter with your right hand only. Notice the angle in your right wrist. Make a putting stroke without the ball and work on maintaining the same angle in your wrist as you move the putter. Keep doing this without hitting the ball until you have the feel of it. Then introduce the ball and actually hit putts with your right hand only, maintaining your right wrist angle. Hit 10 putts like this and then putt with both hands on for two putts, again working on maintaining the angle that you create in your right wrist at set up, throughout the putt. Then repeat this, 10 right hand only putts followed by two putts with both hands.