I think black IPA should definitely have a little roast. Stone Sublimely Self Righteous, Odell Mountain Standard, Deschutes Hop in the Dark, and New Glarus Black Top are tasty commercial examples. I usually use 8-10oz of Blackprinz in mine (for a 4 gallon batch). It's got a touch of roastiness. But I'm looking at giving it more of a chocolately flavor and might put in a few ounces of chocolate malt my next batch, maybe some oats too.