@ the o/p:
When you say that your car rolls, what are you comparing it to? The Dolomite is prone to some body roll which may simply be the nature of the beast in the case of yours, but stiffening it too much for road use will tend to make it less comfortable and far less predictable so a bit compromise is good.
My last one had 190lb springs up front in place of its o/e, 137lb ones which did reduce body roll to a point but it was a lot more pleasant when I'd swapped them back for fresh 137lb ones instead and, roll or no, they have a good bit mechanical grip even when the tyre treads are well and truly distorted, as the following picture from a recent thread demonstrates well I feel:
Now that's a Sprint, but here's a 1300 and the difference doesn't look that great to me, I'd expect your Dolomite to come somewhere between the pair:
Both of those cars are good examples of their type, neither is rolling excessively by the standard of the breed. How does yours compare?