One other thought / clarification. Proper roasted barley is unmalted. But my roast-your-own version, from malt will not matter much here in an extract brew. You'll get the red/brown contribution and roasted taste that the barley would have provided. The chocolate malt suggestion is fair too, but in large qty that can be a bit overpowering and very, very dark. Heck, give both a go sometime - might be better than the original recipe!