If you are going "all into the pool" approach for your mash, then the stout profile would be a good place to start.
Here is the problem that I have with blindly following the stock profiles:
Those profiles are based upon the anticipation of needing some alkali contribution from the water salts to counterbalance the high acidity of the roasted malts (specifically in the case of the stout profile). What it does not take into account and is rarely discussed is that these profiles require all the roasted malts to be used in the mash in order for it to be effective in producing a suitable mash pH. If you cap your roasted malts, or cold steep and add them after the mash, then using these profiles will throw off your mash pH significantly. This is one of the issues I have with the "use this profile for beer colors of X to Y SRM" approach.
There are three reasons to use water salts in significant amounts. The first is to influence how the flavors express themselves in the ending beer. I've mentioned in a post above how the effect of high Sulfates, Chloride, and Carbonates changes how you perceive flavors. Sodium is another ion which will help with enhancing flavors, but you can get too carried away with it and end up with a 'salty' flavor to your beer which wll detract from the overall taste.
The second is for yeast health and beer clarity. The yeast utilize Calcium and Magnesium in their consumption of sugars and turning them into energy and alcohol. They also use the Calcium for aid in flocculation and falling out of solution once the food source becomes scarce. Many sources indicate that they will get enough of these minerals from the malt to properly do their job in converting sugar into alcohol, but a minimum quantity in the water source helps to promote good flocculation and settling.
The third is almost a byproduct of the first two above, which is to help in attaining a suitable pH for enzyme conversion during the mash process. This should steer the types of salts you use to supply the minerals and not necessarily the quantity of the different salts. For instance, for most of us with very soft water, using Calcium chloride, Calcium sulfate, or Magnesium sulfate helps in lowering the pH. Sodium bicarbonate, Calcium carbonate, Magnesium carbonate, Calcium and Magnesium hydroxide will all raise the pH.
Use of any of these should be combined with your specific process to give you the results you want. Although it may not be ideal for dissolution, adding some salts at the beginning of the boil will do just as much for flavor if adding them to the mash water will upset the pH of your mash.
