Prepare the brine by combining the brown sugar and salt with 2 cups of warm water, stirring until salt and sugar are dissolved. Add 2 cloves of minced garlic, one rosemary sprig and the pork roast to a large zip-to-lock bag. Refrigerate for 1 ½ hours.
Remove roast meat from refrigerator 30 minutes before ready to cook. Preheat oven to 325.
Remove the remaining rosemary leaves from stems and mince with the remaining garlic cloves (or crush with mortar and pestle). Combine with olive oil to make a rub.
Heat a stove top griddle or cast iron skillet on medium high heat about 5 minutes
Remove meat from brine and dry with paper towel. Rub with crushed garlic/rosemary mix. Grill one side for about 8 minutes until brown (if your roast has a "fat side" grill that!).
Place meat on roasting pan grilled side up. Roast in 325 degree oven for 30-40 minutes until it reaches 140 degrees internal temperature.
Tent meat with aluminum foil for 15 minutes. Cut into ¼ to ½ inch slices.