1 bone-in pork shoulder butt roast, OR fresh picnic shoulder (8-9 pounds)
3 tablespoons brown sugar, packed
3 tablespoons paprika
1 1/2 teaspoons salt, plus more for sprinkling
1 1/2 tablespoons black pepper, coarsely ground
1 1/2 tablespoons garlic powder
1/2 cup Dijon mustard