It is important to have a paddle that feels right.
That being said, stick with the paddle you have until your technique is solid, like the others said there is no point in getting a new stick until you have the "hip snap" down to a t, as they say in it is all in the hips. See the following link for how to hand roll: How To: Hand Roll a Kayak - YouTube
When you are ready to upgrade our bias opinion would be to pick up one of our new CORE thermoplastic composite blade paddle (the name is still a secret but you can guess the name on our FB page for a chance to win a brand new one). The blades are bomber, the shaft is the strongest on the market and the grips are non-slippery when wet so your hands will always be in the right spot. For whitewater we recommend a bent shaft at 12 degrees, this is the most ergonomic of all options if you learned to kayak with any paddle over 12 degrees.
All the best from CORE!