Remove the pork roast from its packaging and thoroughly pat dry all over. Using a sharp knife, cut just underneath the top layer of fat on the roast to create a pocket of space between the meat and the fat, but do not completely remove the layer of fat. Slash 3 large cuts in the top of the fat layer to allow the marinade to penetrate. Place the roast in a deep roasting pan or large dutch oven.

In a food processor or blender, blend together the pepper, oregano, salt, lime juice and olive oil to create a thin paste. Pour this paste over the pork roast, rubbing some of it under the layer of fat where you created a space. Marinate the pork roast in the refrigerator for about 8 hours, or overnight.

When you are ready to cook the roast, remove it from the refrigerator and allow the roast to come to room temperature. Preheat the oven to 325ºF. Place the roast on a V-shaped roasting rack set in a roasting pan, or on a rack set over a sheet pan and cover the top with foil. Roast for 4 hours covered. After 4 hours, turn the heat up to 450ºF and remove the foil from the roast. Continue to cook the roast at this higher heat until the top has turned brown and crackly, about 10 minutes. Remove roast from the oven, tent with foil and allow it to sit for about 10 minutes before slicing and serving.