Cut the larger tomatoes and onions into chunks. Keep the grape tomatoes whole and add them all to the sheet pan. Drizzle olive oil and a little salt and pepper.
Slice ⅓ off the end of a garlic bulb. Drizzle it with a little olive oil. Wrap the head of garlic in foil and make sure it’s sealed. Place it on the sheet with the cut side up.
Roast the veggies for 40-45 minutes or until they are slightly browned. Flip the onion chunks halfway through if they are charring faster than the tomatoes.