Preheat the oven to 425 degrees F.
In a small bowl, mix together the olive oil, garlic, salt and pepper. Using a pastry brush, spread the mixture all over the pork shoulder.
Set the meat on a rack set into a roasting pan. Roast for 20 minutes, and then reduce the heat to 325 degrees F. Continue to cook until an instant-read thermometer inserted into the shoulder reads 185 degrees F, about 4 hours. Remove the pork from the oven and let stand until cool enough to handle, about 30 minutes.