I can't speak as for how it will affect judging for being out of SRM for the style.
However, I use 8 oz. roasted barley in my hazelnut stout and it is delicious. It gives it a little espresso/coffee flavor.
My SRM calculates to 171.
My only suggested change would be upping the IBU. I use a rule of thumb of IBU/OG of 0.7 to 0.6 for sweet stouts. The lower the number, the sweeter. The higher, the more bitter. Yours is 26/54 =0.48.
Of course, I don't know how that change would put you further out of the style guidelines.
Thank you Lego Movie for letting me know that I'm the serious, unfun, mean dad who never lets his kids play with his toys.
On deck: Barleywine, Dampfbier, Belgain Golden Ale, Hazelnut Sweet Stout, IRA, Rye-weizen, Wit, Uinta Hazel Clone, Uinta Yard Sale Clone.