Heat the olive oil in a large soup pot over medium-high heat. Add the diced carrots, onions, and celery. Sauté for about 5 minutes until the vegetables soften.

Add the diced tomatoes, tomato paste, chicken broth, oregano, and dried basil to the pot. Bring to a gentle boil and let cook for several minutes until the veggies are tender.

Use an immersion blender or a regular blender to puree the soup until silky smooth. Return the soup to the pot.

In a separate saucepan, prepare the roux. Melt the butter over medium-low heat, then whisk in the flour and stir constantly for about 10 minutes until golden brown.

Gradually spoon a ladleful of the soup into the roux, mixing well to form a thick paste. Add more scoops of soup until combined smoothly.

Pour the roux mixture back into the soup pot. Stir in Parmesan, half and half, salt, black pepper, and chopped fresh basil. Adjust herbs to taste.

Cook for another few minutes on low heat until everything is warmed through.

Serve in a bread bowl, pair with grilled cheese, or top with fresh basil or croutons for added texture.