1. Preheat the oven to 400 degrees.
2. Drizzle two baking dishes with olive oil.
3. Slice tomatoes, onions, and red peppers in half. Cut the top off the head of garlic, leaving skin on.
4. Place the tomatoes face down in one dish and the other vegetables face down in the other dish, drizzle with more olive oil and sprinkle with salt and pepper. Roast tomatoes until skin wrinkles and splits, about 30 minutes. Roast vegetables approximately 10 minutes longer or until tender and beginning to brown.
5. Pour tomatoes and their juice in a pot, adding the vegetables when they're ready and squeezing in roasted garlic. Blend with an immersion blender to desired consistency.
6. Add pepper, thyme, hot sauce, lemon juice, and tomato paste. Let simmer.
7. Boil orzo until al dente and toss with sauce.