I find that keeping the sulfate level relatively low is a good thing in roasty beers. Sulfate’s effect is rather drying on the palate and so is roast flavor. Therefore, I find that the flavor and perception can be reduced by adding a bunch of gypsum. Keeping the sulfate below 100 ppm seems to work for me. Trying to achieve an appropriate mash pH via large calcium salt additions has not proven to be a good way to produce good tasting beer.
All things in moderation!
