Position a rack in the middle of the oven and preheat to 400°F.
Place the tomatoes and garlic on a parchment-lined sheet pan. Toss with 3 tablespoons of olive oil, ½ teaspoon of salt, the sugar, and 1 teaspoon of dried oregano. Roast in the oven for 15 minutes.
While the tomatoes are roasting, start the soup. Place 2 tablespoons of avocado oil, the onion, and carrot in a large pot over medium-low heat. Cover and cook for 5 minutes. Add the celery and leeks, cover, and cook an additional 3 minutes, stirring every so often.
Add the tomato paste and stir well to coat the veggies, then add the rosemary, thyme, bay leaves, red pepper flakes and leftover dried oregano. Stir to combine and cook for 30 seconds.
Add the roasted tomatoes and garlic, along with their juices, plus the chickpeas and stock. Turn heat to medium-high and bring to a boil, uncovered, then turn heat to low, cover, and let simmer for 20 minutes.
Take out the bay leaves and discard. Add the salt and white pepper, then puree the soup in a blender until completely smooth. Taste and adjust seasoning, if necessary.