Preheat the oven to 325ºF. Line a baking sheet with parchment paper and arrange the tomato slices in an even layer. Drizzle with olive oil, season with salt and pepper, and sprinkle evenly with the crushed garlic. Bake until the tomatoes have released a lot of their moisture and are beginning to brown slightly, about 65 minutes.
Meanwhile, heat a panini press to medium high. Spread the inside of all the bread with pesto, then place one slice of mozzarella on the bottom piece of bread, add 4-6 tomato slices, and top with one one slice of provolone. Replace the top piece of bread and grill sandwiches, in batches if necessary, until crusty and melted, about 5 minutes.