Place the berries on a pie tin and roast for 10 minutes. Pulverize them in a spice mill with the cinnamon and nutmeg. Place the spice mixture in a food processor, fitted with a metal blade. Add the scallions and chile. Season with salt and pepper. Process until a paste is formed. Add the rum and mix well. Rub the mixture all over the pork loin. Cover and allow to marinate for at least 1 hour at room temperature.
Increase the oven temperature to 400 degrees F.
Remove the meat and place in a roasting pan, and roast for 30 minutes. Reduce the heat to 350 degrees F and continue to roast for 1 1/2 hours, basting every 30 minutes. Remove from the oven and rest for 5 minutes before slicing. Serve with the Island Beans and Fried Plantains.