can you get replacement springs that are stiffer to control body roll without having to lower the car ???

Srings per se will have very limited effect on roll. You need to beef up the roll bar to reduce roll although lowering will have some effect. I think you might be able to do this with an Alfa part depending on the model of your car.

To sound like an old git if you are worried about roll in a brava then you are driving too fast for a public road, especially if your concern relates to roundabouts. it will roll more with more passengers, a reminder to slow down. They won't be impressed if you ditch it or worse. We all went a bit too fast when we were young, some regret it, most slow down a little.