Start by preheating your oven to 380F and lining a baking tray with parchment paper.
Cut the small pumpkin in four. Scrape out the insides and peel the exterior skin. Chop the prepared pumpkin into chunks and place on the lined tray.
Cut the tops of the garlic bulbs, to expose the cloves, and place them on the tray. Peel the onions and cut it in quarters. Cut the celery ribs in 3 inch pieces and place them, and the onions on the baking tray.
Drizzle 2 tablespoon of the olive oil over the vegetables. Sprinkle on 1 teaspoon of the salt.
Cut the Roma tomatoes lengthwise, and place in a 9"x13" baking dish. Drizzle with 1 tablespoon olive oil and then sprinkle with the 1 teaspoon of salt and the oregano.
Place the veggie tray and the tomatoes in the preheated oven. Bake for 50 minutes.
Remove the roasted garlic bulbs from the tray to cool. Transfer the roasted veggies and tomatoes to a Dutch oven or soup pot. Squeeze the garlic cloves out of the bulbs and into the pot.
Add the broth to the pot and simmer for 15 minutes. Whisk in the tomato paste into the soup and then use an immersion blender to puree the soup.
Serve the soup with a dollop of sour cream, fresh chopped cilantro, and roasted pumpkin seeds.