There aren't any "cons" to their use, only "pros". Should your soil be deficient in them, the rose roots won't absorb nutrients as efficiently as they will with them. If your soil has its appropriate concentration, you probably won't notice any improvement. Therefore, the only drawback to adding them is, if you already have them, you'll be spending however much they cost where you are, for little to no visible benefit. Go for it, it couldn't hurt!