Preheat oven to 350°.
To prepare butter, remove white papery skin from garlic head (do not peel or separate the cloves); drizzle with oil. Wrap head in foil. Bake at 350° for 1 hour; cool 10 minutes. Separate cloves; squeeze to extract garlic pulp. Discard skins. Combine garlic pulp, mustard, and butter in a small bowl; set aside.
To prepare sandwiches, scoop out inside of roll halves, leaving a 1/2-inch shell. Spread about 2 teaspoons garlic butter over cut sides of top and bottom halves of each roll. Arrange pickles, turkey, ham, and cheese evenly on bottom halves of rolls; top with top halves.
Heat a nonstick grill pan over medium-high heat. Coat pan with cooking spray. Add 2 sandwiches to pan. Place a cast-iron or heavy skillet on top of sandwiches, and press gently to flatten. Grill 4 minutes on each side or until cheese melts and bread is toasted. Repeat procedure with remaining 2 sandwiches. Cut the sandwiches in half diagonally, and serve immediately.