Mash garlic into paste in a mortar and pestle or pilon. Transfer to a bowl; mix in salt, 1 tablespoon oil, oregano, black pepper, adobo seasoning, and vinegar.
Lift skin off the pork to 1-inch from the narrow part of the bone. Make 3/4-inch slits all over the pork with a sharp knife. Stuff seasoned garlic paste into the slits. Pull skin back over to cover the pork.
Mix remaining 1/2 teaspoon oil and sazon seasoning together in a small bowl. Rub over the skin of the pork.
Transfer pork to a large roasting pan. Pour in beer. Cover with aluminum foil, sealing well.
Roast in the preheated oven until slightly pink in the center, about 3 hours.
Increase oven temperature to 350 degrees F (175 degrees C). Uncover pork and continue roasting until skin is golden brown and crispy, about 2 1/2 hours. Remove from oven and let stand for 10 minutes before carving.