Toss to combine tomatoes, sea salt, red pepper flakes, and olive oil in a 9 x 13-inch baking dish. Tuck garlic cloves (still in their papery skin) into the tomato mixture.
Roast 20 minutes. Press garlic cloves, and if tender and soft to the touch, carefully remove from tomato mixture and set on a cutting board to cool. If using larger cloves, they may need the full 30 minutes to cook through. Return baking dish to the oven and roast 10 minutes more.
When cool, squeeze garlic from papery skin, mash with a fork, and stir into marinara once it's out of the oven.
Meanwhile, cook spaghetti to al dente in a large pot of salted water. Remove pasta from water (or if using a colander, be sure to reserve 2 cups pasta cooking water), and set in a large bowl. Use a silicone spatula to scrape tomato sauce over the spaghetti, and toss. Add several splashes pasta cooking water as needed. Add fresh herbs, torn burrata (if using), and sea salt and red pepper flakes to taste. Garnish with fresh herb sprigs and cherry tomato clusters. Serve immediately.