Read several posts about chocolate stouts and it seems that using nibs as a secondary flavoring without adding to the boil is the consensus. Roasting them first has been suggested, as well as soaking them in vodka. My question is how long should I roast them and at what temperature? What I have are cracked nibs from a chocolatier here in Seattle, do they need to be soaked in vodka? Thanks in advance.
For most spices and nuts, you roast them just until they become aromatic. When I roast almonds I do them in the oven at 350F for 5-10 minutes, and then let them cool. Remember that dry things like that will maintain their heat for a good long while, and they will continue cooking (carry-over) for a few minutes after you remove them from the heat. There's also a short window between roasted and burned.
You can also do them in a dry skillet, as mentioned in this question: What technique best infuses spices into a dish?
I did a coffee imperial stout that I use nibs in secondary. I did not roast them but I don't know how much the ones you have will differ from mine. These are the ones that I used. http://www.surlatable.com/product/PRO-24981/Scharffen-Berger-Cacao-Nibs
The flavor after about 3 weeks in bottles was more of a bitter, unsweetened, dark, 100% cocoa flavor more than a cheap Hershey's bar. (Personally it worked well but maybe the wrong chocolate flavor for a cider.)
As far as vodka: I tried soaking mine for a few days to try and extract more flavor but the whole mix just ended up smelling like bad vodka I wouldn't want in my beer. I ended up just using enough to cover the nibs long enough to disinfect, then drained the vodka off.