Preheat oven to 450°F. Toss tomatoes with 2 tablespoons olive oil, thyme, salt, pepper and half the garlic on a rimmed baking sheet. Roast until tomatoes burst and char, 15 minutes. Reduce heat to 375°F.
Heat a 10-inch nonstick skillet with a drizzle of oil over medium-high heat. Add bacon and brown until evenly crisp; drain bacon on a paper towel-lined plate. Wipe out pan, return to heat and melt butter. Add potatoes and season with salt and pepper. Stir to soften and very lightly brown the potatoes, 5 minutes. Add leeks and garlic, and stir, 3-4 minutes more.