Hello Steve welcome to the forums. So you want an 85ish frame but want gearing more like the early '90s. There is actually a whoe thread dedicated to this type of project. The only thing you really need to do is find a good shop to coldset (spread and realign the rear dropouts) and your good to go.

The hard part will be finding a frame, Rossin is one of the names that like DeRosa, Colnago, and Bianchi command a preium for nice ones. And actually I see far more Colnagos for sale that Rossins. I don't know if that means they sold many more Colnagos or Rossin owners don't part with them.

Look over this thread for some inspiration http://www.bikeforums.net/showthread...ldies+with+sti

Some of us go the other way and take a new frame and build it 'old school' http://www.bikeforums.net/showthread...ldies+with+sti