For the pork roast: Preheat oven to 350°F. In a small mixing bowl add chopped rosemary and spices. Slowly drizzle in olive oil and whisk until blended. Rub spice marinade all over the prepared pork shoulder roast (marinate a minimum of 2 hours). Place in roasting pan on rack, add water to bottom of the pan, cover with foil, and let slow cook for 3 1/2 to 4 hours at 350°F, or until internal temperature reaches 165°F. Remove foil.
For the glaze: Place cane syrup, pan juices, vinegar, mustard seeds and Dijon mustard in a saucepot. Turn heat to medium high and stir to blend well. Reduce heat to medium and simmer 25 minutes or until mustard seeds become soft. Set aside. To glaze: Apply glaze with a brush or spoon and spread evenly all over the pork. Bake for 10 minutes. Repeat glazing 2 more times, baking 5 minutes between glazings for a total of 20 minutes. Remove from pan and place on a serving platter for carving. Let rest 15 minutes before slicing. Serve with remaining glaze.