While rosemary and thyme are both popular herbs used to flavor many dishes, they are not always interchangeable. Both possess a distinct flavor that can stand alone in a dish, though they differ in both taste and intensity. Rosemary has a more robust flavor and pairs especially well with beef, lamb, pork, or game meats. Thyme has a much milder taste that works better for poultry and fish dishes. Many substitute rosemary for thyme of necessity when it is not available, but to get the best flavors from any dish, it is best to use the herb called for by the recipe.