Place tomatoes and garlic on a parchment-lined baking sheet and drizzle with olive oil. Shake the sheet to coat the tomatoes and spread them out into a single layer.
Sprinkle generously with kosher salt and pepper. Roast for 15 to 20 minutes, until the tomatoes are soft and one or two have burst their skin.
Transfer the tomatoes to a serving platter and sprinkle with basil if using, and another light sprinkle of salt. Serve hot or at room temperature.