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