I used the info in Ray Daniels' book "Designing Great Beers" to make my brewing salt calculations. Your LHBS may also have some salts that you can add to RO water.
I also use RO water since our local water is high in Arsenic. I use a combination of calcium chloride, table salt, baking soda, gypsum and epsom salts.
Fermenting: Grand Cru, Belgian Dubbel, Nut Brown Ale, Saison Sans Soul
Kegged: Honey Amber Ale, Centennial Blonde Ale,
Gone but not forgotten: Irish Red