Pilates has a specific order of exercises and each is done in a certain amount of reps. Each exercise has a purpose and goal. Rolling like a Ball is done in a compact ball shape and is meant to massage the spine and rid the body of toxins. In performing each exercise in the series the student must have this understanding in order to have discipline in their form. Quick and efficient transitions also count when it comes to precision. Your workout needs to have an even tempo and flow to utilize your time.
Make sure in each session you push yourself and gain a deeper understanding of the method that will lead you toward your ultimate goals. Good health and fitness always come first. Modifications can be made or props added, but make sure the true essence of Pilates remains.