Assuming you are successful at roll number 12, the Storm Roll, then rolling with your arms crossed becomes a very useful roll to practice. I find this roll useful not because your arms are crossed but because it decreases your dependency on heaving up on the paddle. Decreasing your dependency on the two handed heave will eventually cause you to improve your Storm Roll to a point where the paddle is just coming along for the roll and is not being used as a huge lever.
In reality I cannot imagine a practical use for this roll in a combat situation, but it does help as a training aid. It can also be fun to try this one handed. Try alternating which hand you use for maximum training benefit.
Click on the photo or this link for instruction and video of rolling with hands crossed.
