I think you will be quite disappointed with the size of Delawares at 10-12 weeks, you certainly won't have a roaster.
I recently butchered an 18 week old Delaware cockerel that dressed out at 4 lbs 2 oz. I took the meat off the bones, breaded and fried it. It was delicious and plenty tender. This bird would not fit my definition of a roaster despite its weight. It's not proportioned like I envision a roaster and there wouldn't have been much space for stuffing. A 4 lb 2 oz Cornish Cross meat bird would have been plumper, rounder, fuller (and had smaller legs and thighs).
I have reason to believe the Delaware that I butchered was on the large size of what is typical for the breed; at 16 weeks his live weight compared favorably to the weights achieved by at least one person who has been breeding for size for 5 years.
While I would not roast a Delaware (since it's all about the stuffing for me), I would certainly eat another. In fact, this experience has left me encouraged about using dual purpose breeds for meat. Just not roasters.