So basically an imperial stout? I'd hardly say they're sweet, but they're not exactly dry either. Not sure on if you're able to do a mini mash, but AFAIK you need to mash flaked oats with barley for the enzymes to convert. Hopefully someone with a little more knowledge than I can chime in to be sure. But that aside, a good selection of specialty grains is:
1.25 lb Roasted Barley
1.00 lb Flaked oats or barley (if this will work with steeping or you can do a mini mash)
1.00 lb Special B
0.50 lb Carafa III
0.50 lb Crystal 60*L
Not sure what type of extract you'll want to use with that, but basically add enough to hit an OG of ~1.100, you won't be finishing below 1.020. That should net you ~10% abv when everything is said and done. I have a RIS aging in secondary that used 16 lbs of 2-row along with those grains (flaked barley, not oats) and it tasted damn near Old Rasputin when I was racking it over.
As for hops, I'd aim for about 60-70 IBUs. I prefer Willamette for the late hopping (usually a 15 and KO addition), bittering really doesn't matter what hop you use. Something high AA and cheap
.
If you do want to include oatmeal, I would really look into doing a BIAB partial mash. I've never done one, but by my understanding it's pretty easy and all you really need is a grain bag to put your specialty grains in, along with an amount of 2-row, hold that at mash temps for about an hour, then proceed along with brew day as normal.
Oh, and do pitch enough yeast and get ready for an explosive fermentation. I racked mine onto an S-05 yeast cake from a 1.057 oatmeal stout and it nearly blew the lid off the bucket.
