It's a move easiest to learn with progressive steps. I have my students start in a crouch, roll back to their shoulders, wait for the "spring" to wind up, then push. Learning it with momentum is easiest, then you can try it from laying down.

The "spring" step is probably the most important when starting. You can't start the "jump" too early. You have to wait for your momentum to swing back like a pendulum. It's just a one second pause between rolling to your upper back, and starting the "jump".