Well to start off, you definitely need both hands on the handle when doin this trick. Since the backroll is a load and release invert the flip really focuses on the pull of the boat to do the rotation.
So to start off, cut out about the same distance you would for a normal wake jump. Take a mellow edge into the wake, then once you have almost reached the wake really load the line, which means put alot of pressure on your edge at the wake. You will need to keep the handle in close to your body, so try to touch your elbows to your sides. Make sure to edge all the way through the wake, and also make sure to stand tall at the top of the wake. This doesnt mean stop edging, keep that strong edge through the wake while you stand tall. Then once you are leaving the wake look over you lead shoulder, and your rotation will start. Also again make sure to never let the handle away from you body while doing the rotation, if you let the handle out during the rotation you will come up short. When you keep the handle in close it speeds up the rotation, so make sure to do this. When you spot the water over your lead shoulder get ready to land. It is definitely better to over rotate this trick than it is to under rotate, but if you do find yourself over rotating it, when you spot the water slowly let the handle out again. Also to prevent yourself from going to revert let the handle out towards the flats when you land. Remember, do not try to throw this trick off of the wake. It is a load and release invert, so the boat should do most of the work for you as long as you do what I said above. Hope this helps.