Step 2) Combine rub ingredients in a medium size bowl and stir well. Remove 1/4 cup to a separate bowl,cover and set aside.
Step 3) Place roast in a large dutch oven or roasting pan. Coat thoroughly with half of the rosemary rub.
Step 4) Add potatoes, carrots and onions to the remaining corn oil and toss to coat. Pour potato and carrot mixture into roasting pan with pork roast. Cover and place in oven for 45 minutes.
Step 5) Remove lid, drizzle roast and vegetables with orange juice and peel and continue roasting for 45 to 60 minutes, or until top is browned and pork is cooked through.
Step 6) Remove from oven and allow to rest for 5 to 10 minutes. Transfer roast to a cutting board and slice across grain into 1-inch thick slices.
Step 7) Drizzle sliced pork with reserved 1/4 cup of the rub, garnish with sprigs of Italian flat-parsley, if desired, and serve with roasted potatoes and carrots.