Preheat the oven to 400°F (200°C). Line a large baking tray with parchment paper or a nonstick silicone liner.

Toss the tomatoes and bell pepper with 2 tablespoons of the olive oil and 1/4 teaspoon of the salt.

Spread out in single layer on the baking sheet, and roast for about 1 hour. Toss them a few times during cooking so that they roast evenly. 

In a large pot over medium-high heat, warm the remaining 2 tablespoon olive oil and sauté the onions and garlic with 1/4 teaspoon of the salt for about 5 minutes, until soft and translucent.

Add in the carrots, broccoli and zucchini and sauté for a further 5 minutes until just softened.

Add the roasted tomatoes and peppers and their juices, the canned tomatoes and their juices, the vegetable broth, fresh basil, and sun-dried tomatoes with 1/2 teaspoon of the salt and bring to a boil. Reduce the heat to medium, and simmer partially covered for about 20 minutes to allow the flavors to infuse. 

Allow to cool. Add in batches to your blender, and blast on high for 30 to 60 seconds until smooth and creamy. 

Return to the stove, and add the remaining 1/2 teaspoon of salt to taste, and season with freshly ground black pepper.