Would one ounce of roasted barley (450L) impart a noticeable flavor/astringency in a five gallon batch of American Amber Ale?
No, one ounce is really little. You'll get some darkening but that's about it.
I used 2 ounces in my amber and it adds a nice toastiness in combination with other dark malts but you will not be able to taste roasted barley per sehttp://www.homebrewtalk.com/f66/tortures-damned-289473/
I can taste it. Carafa Special imparts less flavor.