To roll out your Psoas, a big foam ball/posture ball works best. Place the ball in your abs above your hip to one side of your belly button.
Relax over the ball and lie face down on the ground. Breathe.
Then move the ball, working your way around the side of your lower abs between your belly button and hip. After you move the ball, relax completely back over it.
If you don’t have a larger ball, you can use a tennis ball; however, the tennis ball will dig in more. To use the tennis ball, you will also need some books or a yoga block. Place the ball up on the books or block and lie over it just like you would with the posture ball. Relax and breathe.