Originally Posted by mark_vanis
The number one thing that helped get (and keep) my role is staying calm under water
This is key. I still panic sometimes, and afterwards am upset with myself for not staying cool. Not only do you use less oxygen when you stay calm, but you think clearly and roll with better form. This should be the golden rule of upside-down boating. I'm still learning to do it, and it seems like it only comes with experience and spending a lot of time upside-down.