Use dense, thickly cut white bread and double-smoked, black-pepper or other flavorful bacon-it should be thickly cut, too.
Heat oven to 375 degrees. Rub entire head of garlic with olive oil. Place on aluminum foil, add herbs, and wrap tightly. Cook until cloves are soft, 25 to 35 minutes. Set aside to cool. Squeeze roasted garlic out of each clove onto a cutting board. Transfer soft garlic to a medium bowl; mash with a fork until smooth. Stir in mayonnaise, and set aside.
Working in batches, fry bacon in a heavy skillet over medium heat until crisp. Transfer bacon to paper towels to drain. Toast bread under a broiler until lightly golden on both sides.
Spread one side of each bread slice with garlic mayonnaise. Arrange lettuce over two slices. Top with tomatoes and bacon. Season with salt and pepper. Top with remaining bread slices, and serve.