This depends on whether we’re talking about brushing on an egg wash or brushing on butter. An egg wash (not used in this recipe!) is intended to give rolls or bread a shiny, golden brown color as they bake. Brushing on butter after rolls or bread bake gives them a buttery sheen but doesn't darken them in color. Of course, the butter also makes them even more buttery (yes please). You don’t need to brush these easy yeast rolls with butter after they come out of the oven, but far be it from me to stop you!