-- Last Updated: Feb-01-13 2:58 PM EST --
Until you learn to reliably hand-roll, I don't think you will know how to roll "well". The reason is, that with a hand-roll you have very little leverage on the water. Just to manage a hand roll you need to have all your technique just about perfectly lined-up or you will fail.
So, in the process of learning to hand-roll you will clean-up your technique. The bonus is that if you lose your paddle or it breaks, you will still be able to roll-up, usually ...
Oh, and that said, try not to roll unless really necessary. Especially with hard and sharp objects underwater near you. Learn reliable low and high brace. Even if the brace fails, before you go under and as soon as you hit the water flat on your side, you should still be able to rollback-up from there without having to have to roll under the boat.