What about the rear? That's where I see the problem on tight curves.
We have a pretty nice sized one there, the antiswaybar. I believe its the same size/thickness as the adjustable, but I never measured. Rob said the Elises and Exiges never came with a rear antisway bar in the rear, and I also believe that he said that the front swaybar was smaller than the Roadster's too. I could be wrong, never compared them.
I feel the Roadster is fine on the street if properly setup. My front hooks up amazingly and the rear sticks right in there, your negative camber is a huge influence with this. Also I'm not feeling any bodyroll that's of any concern nor needs to be addressed with the Nitrons. If that's a worry, one could lower the Roadster some with the adjustable suspension. If you want more bite up front, you can play around with the camber and with the relationship between the front and back traction. But like any tuning, you have to understand what your modifying, and how it affects the overall performance of the car and learn how it behaves in multiple conditions and inputs.
The roll I feel is the Aluminum frame flexing, its called cowling. Since our sills / tub was cut down lower for easy entry, we lost a serious frame support that helps stabilize the side to side and twisting and flexing forces the frame undertakes. Putting in a full rollcage would help stiffen the frame back up. The twisting flex takes its toll on handling, takes away from some contact ability the tires have to the road, and also diminishes the input the driver receives front the car from the wheels to and through the steering wheel as well as the way the body is connected to the ground in terms of feel for the road.