If by roach you mean a convex leach, that's easy to accomplish but the performance gains are minimal. Doesn't add much at the head, doesn't add much forward thrust. Does smoth out exiting air flow. You will need longer, better battens to hold the fabric out.
The greatest gains in roach are made at the sail top -- going from a pointy head to a squared-off or
PowerHead. That's where the wind is strongest and where your present sail is least effective. Two full-length battens would do ya. But unless you crane out your backstays, you may catch. (Our Bucc18 uses a powerhead. It's nice.)
If you live in a light wind area, you might profit better by ordering a main with deeper draft and/or full-length battens. As I mentioned before, the trouble on that cute keeler is gonna be controlling the slot. I'd focus on getting your main and headsail sheeting and twisting just so. That'll increase drive more than a couple sqft of fabric on the trailing edge.
