Sprinkle roast with salt and pepper, and rub with 2 tablespoons brown sugar. Place in a Dutch oven, and add 2 cups water. Cook, partially covered, over low heat 2 hours or until tender. Remove roast, and shred.
Bring remaining 2 tablespoons brown sugar, ketchup, and next 6 ingredients to a boil in a heavy saucepan. Reduce heat, and simmer 15 minutes or until thickened. Stir in shredded roast. Serve on hamburger buns.