For quicker flavoring from cocoa nibs, make a tincture with a neutral, high quality vodka. Take 4 oz of cocoa nibs, put them in a container, and then add enough vodka to cover. Every couple days, shake the container. After a week, you've got a homemade chocolate extract. Add to the bottling bucket or keg to taste.
BTW, some cocoa nibs are unroasted in the package. If the one you buy is unroasted, throw them into a small skillet, and roast over medium heat, moving them constantly. They'll start to brown up, and that's time to pull them off the heat.