Hm. How stout-like do you want this? I made a stout last year I really enjoyed based on a well-respected Shakespeare Stout clone that included (for 5 gallons, note) 1.25# Chocolate malt and 1# Roasted Barley. I only say that to make sure you're getting the roasty stout-ness you want. And I recall beergoggles mentioning a recipe he did for a coffee stout (or was it a porter...) that had 2# black patent. So the roasty grains seem to be a bit low if you're looking for something dark and roasty. Usually, American brown ales have about 0.5# chocolate malt per 5 gallons, just as a data point.
I'm looking for others to throw in some input too, but that's my 2 cents. Best of luck.