I first learned to roll not in a Parkour class, but in a bushido class. In that class our warm up was rolling. We would spend about 10 minutes in the beginning of the class working rolls. We did front rolls, back rolls, side rolls, and dive rolls. We trained rolling over things. We trained tripping into rolls. We even trained side rolls where we would try to maintain eye contact with a target. In bushido rolls are used to either safely exit a grapple, protect against an unpredicted fall, or cover a small distance in a tactical way. In parkour we use primarily front rolls. From time to time we will train back rolls, but we rarely apply them. Rolls in parkour are used for passement (passing), covering a gap, moving quickly under an obstacle, and are most known for distributing force in a big landing.
All of rolls we teach are the same movement just applied to different situations. The rolls are similar to a gymnastics front roll but performed on a diagonal. We use one arm as a guide that leads into the upper shoulder. Then a line is traced down across the back to the opposite hip. This line is the path of contact with the ground. We come out on the far side of the roll in a low crouch. In a dive roll we dive out the hands make contact first and then we complete the roll maneuver. In a passement roll the size of the obstacle dictates the way the roll is performed. If the obstacle is smaller the hand and arm guide may be skipped and we transition straight to the back across the body. On a larger obstacle the roll will be done in the same way as a dive roll. The most ubiquitous application of the roll is the roll landing. The roll landing is applied to a big drop. If the impact from a drop is going to be more force than the body can safely absorb in a two-footed, three-footed or a slap landing, a roll is employed. For the roll landing, we land with two feet and continue to fall until the body is at roughly a 45 degree angle to the ground and the legs are bent 90 degrees at the knee. Then the upper body is tucked and the roll is employed.
The other key use of a parkour roll is in a bailout. When something goes wrong, in any manner, during a parkour movement, a roll can help. On countless occasions I have seen people I train with make a mistake in a technique and employ either a front or back roll to save themselves. This application is more similar to the use we learned in martial arts. The problem with teaching the roll for this situation is that it’s unplanned. All the practitioners who I have seen saved by rolling out on a bail were longtime practitioners. They are people who have performed hundreds or thousands of rolls, and the movement is done instinctively. For this reason I think it is vital to teach the roll as part of a bail technique. Learning to roll from kneeling following by standing then dropping is great. However, as much time should be applied to learning to do a roll in a direction in which we are not looking or on command when we don’t expect. It’s difficult to train spontaneous use of a technique; however, that does not mean it should not be attempted.
Though the roll is a safety maneuver, it can be dangerous. The big problem everyone runs into is cracking shoulders and hips on the hard ground. With good technique and practice, these parts can be protected. Tips for avoiding them include making as little contact with the ground before reaching the upper back. There is an additional technique we employ in teaching of rolls now that involves rocking back and forth on the ground to find the soft tissue pathways across the body. Another issue can be foreign objects on the ground. Always check your surfaces! Finally, backpacks. This is an issue for everyone. Everyone who trains parkour wears backpacks all the time for EDC (everyday carry). Rolling when wearing a backpack is painful. There is not much that can be done about either of these last two problems with an accessory on your back. Train your rolls in a "safe" environment. That way if you need to use them in real life, you are far more likely to execute the roll safely.
Rolls are iconic parkour movements. When people invision parkour, the roll is one of the first movements that come to mind. They are graceful and beautiful. Rolls can be employed to achieve many goals in many situations. They are also one of the most difficult movements to perform in a multitude of situations. Mastering a roll on any surface at any speed will enhance your skill as a parkour practitioner exponentially. Not only do they add grace and flair, but they can save your life or at least your limbs.