I'd call it a stout if the abv is high enough, but what's in a name?
FYI: Schwarzbier and cerveza negra mean black beer and are generally lagers, not ales like stout. Trouble is, they're generally more dark brown than black. Once upon a time the Brazilians brewed really black and very roasty lagers under the brand names Caracú and Xingu. Today's Xingu seems to be less black and roasty than what I remembered, whilst Beer Advocate now describes Caracú as a milk stout. BJCP says many Baltic "porters" are actually lagers.
Go ahead and use your insane 12% roast barley and play away. If you also throw in so much crystal it pours like syrup, call it a London stout. If the OG is up in the 1.08 range, say Baltic porter. Or use a lager yeast, make the IBUs 15-20, the abv @ 4.5, lager it and invite all the elderly North Coast Brazilian expats over for a taste of cerveja negra autentico. Seriously, those old black beers were damn good.
Edited by yankinoz, 30 December 2016 - 06:55 PM.