It's a little difficult to tell, but the client pictured here has her arms overhead, holding onto a dowel rod attached to the mat. These mats are raised padded platforms that have handles at one end and usually a foot strap at the other end. The handles make some inversion Pilates mat exercises (rollover, corkscrew, jack-knife) quite a bit easier. And the foot strap would have abolished my difficutly with roll up.
If you don't have access to one of these, you can simulate the handles with the uprights on a trap table or reformer with tower.