Preheat the oven to 350 F. Rub salt, pepper and olive oil all over the roast. Place in a cast iron pan or roasting pan. Roast for 30 minutes.
While the roast is in the oven, combine the cranberry sauce, butter, brown sugar, apple cider vinegar, orange juice and zest, dry mustard and rosemary in a medium saucepan and whisk over medium-low heat until butter is melted. Simmer for 10 minutes. Remove the rosemary and take off heat.
Baste the roast with the glaze and return to the oven. Bake another 15 minutes and brush with more glaze.
Stick a meat thermometer into the center and return to the oven for a final 5-15 minutes, or until the thermometer registers 145 F.
Remove from the oven, brush more glaze onto the roast and let it rest for 5-10 minutes, removing the strings before slicing.
While the roast is resting, pour the pan juices into the remaining glaze, season with salt and pepper, and reheat gently. Serve with roast.
Before cooking, bring the roast to room temperature. Take it out of the fridge at least 30 minutes and up to an hour before putting it in the oven. This will ensure that it cooks evenly.
You can count on approximately 20-25 minutes per pound to cook a pork roast, but it's always best to use a meat thermometer and take it out of the oven when it reaches 145 F.
After cooking, allow the roast to rest for at least 5 minutes before slicing into it. This allows time for the roast to finish cooking and for the juices to redistribute throughout the meat.
When choosing a roast, figure about 1/2 lb per person. So a 3 lb roast will feed 6, while a 2 lb roast will feed 4.
Leftover roast can be stored in the refrigerator for up to 3 days and is absolutely wonderful in sandwiches.