I've never done something like that but in the Mar/Apr 2012 Zymurgy magazine, there is a recipe for Chestnut Brown Ale. The brewer adds 1lb of chestnuts to the grain bill (9lbs other malts) for a 5 gallon batch. He roasts them at 350F (177C) until the nutty aroma develops, then smashes them with a hammer (probably under some paper towels), and runs them through his coffee mill. He adds the chestnuts to the mash.
Hope that helps,