The easiest way to grab your back roll is a nose grab or a "fake" method grab which is grabbing the board on your heelside edge close to the nose.
what you want to do is cut at the wake a little softer than you do for a normal back roll. when you leave the wake initiate the back roll and push your back leg staight and suck your front knee up towards your chest as much as you can. start reaching for the grab right off the top of the wake. if you do this right the board will fall into your hand. hold the grab as long as you can and when the board starts pulling you to revert push the handle towards your front hip. land and ride away
Brett Brinkerhoff firstname.lastname@example.org