Make slits all over roast and insert pieces of fresh garlic. Juice 2 oranges and 2 limes. Mix together orange juice, lime juice, and 2 tablespoons olive oil. Place pork in a large re-sealable bag or in a glass dish. Pour the juice mixture over the pork. Turn to coat. Seal bag or cover dish and refrigerate for 24 hours. Remove roast from marinade. Pat dry and place in a roasting pan. Drizzle roast with the other 2 tablespoons olive oil. Season well with salt, pepper and oregano. Bake in a preheated 350 degree oven in a roasting pan for about an hour or until it reaches an internal temperature of 145 degrees. Cover with foil and let rest 10 to 15 minutes before slicing. You can also grill the roast. Serve the pork with lime and orange wedges or slices.
You can also grill roast. Grill on direct heat for a 3 to 5 minutes on each side or until nicely seared. Then move to indirect heat and grill until internal temp of 145 degrees.