Preheat your grill and prepare for an indirect cook.
Drain olives and capers. If the olives contain pits, go ahead and remove them.
In a food processor, blend together the olives, capers, mustard, garlic, oregano, and black pepper, until smooth. Set aside.
Butterfly cut the pork loin and lay flat onto a large cutting board. Spread the tapenade mixture evenly over one side of the pork loin, then roll and tie it securely with kitchen twine.
Combine the herb crust ingredients and apply all over the surface of the tied roast. Place roast on grill and cook for 1 ½ hours, or until the meat reaches an internal temperature of 160 degrees F. Since there is a filling, you'll need to cook the roast to well done.
Once cooked, remove from grill, and let the grilled pork loin rest for 5-10 minutes. Using a sharp knife, slice into 3/4 inch pieces. Serve immediately with your favorite sides.