Last year I brewed the dry stout from Brewing Classic Styles and it wasn't roasty at all until it had cold conditioned in the keg for a couple weeks. Out of the fermenter it was closer to a mild than stout. I'd say leave it as it is and wait for the yeast to drop out. If you really want to mess with it, don't do it to the whole batch - bottle half then add the extra roast to the bottling bucket for the last half. I'd bet that if you did a side by side with the original and extra roasty, you'll like the original more.