Preheat oven to 375 degrees F. Trim fat from pork tenderloin and season all sides with sea salt and pepper. Heat olive oil in large skillet over med-high heat, once heated add pork and sear until golden brown on all sides and set aside. Lower heat in skillet to medium-low and add balsamic vinegar, fresh blueberries, and rub. Scrape up any browned bits stuck to the pan from the pork. Let simmer for a few minutes to thicken. Place pork on a roasting pan or rimmed baking sheet and coat with glaze. Roast for a total of 20 minutes. If you have any remaining glaze, brush over pork half way through roasting time. Garnish with fresh rosemary before serving.