Without giving it much thought, I've always roasted garlic for use in cooked preparations (hummus, spaghetti sauce, garlic bread, etc.), and used it raw for uncooked preparations (salad dressings, tzatziki sauce, etc.).
Cooking with friends recently, one said all that matters is how much or little garlic pungency you want in that dish; another said the acidity of the other ingredients in the recipe dictate which form tastes best (raw with tart or acidic flavors; roasted with more salty and savory flavors).
Of course, personal taste preferences will nearly always trump cooking traditions and rules of thumb, but is there science or logic behind choosing which form for a particular dish? Other than roasted garlic being milder and sweeter than raw, does either go with a particular cooking method or set of ingredients better than the other?