Heat oven to 400 degrees. Arrange tomatoes on foil lined pan brushed with olive oil. Brush tops of tomatoes with olive oil, then sprinkle with salt and pepper. Roast for 30 minutes.
Heat a few tablespoons of olive oil in the bottom of an extra large stock or soup pot over medium high heat. (I actually use two (2) standard-size stock pots.) Add onions and sauté until lightly golden and tender, about 5 minutes.
Reduce heat to medium and begin adding additional vegetables, 1 at a time, stirring well to ensue all the vegetables get coated in the oil. If you are using more than one pot, divide the vegetables equally among them.
Add water or broth and potatoes, stirring well, the add onion soup mix, salt, & pepper to taste. Bring to a boil, then reduce heat to low, cover, & let simmer for at least an hour. Store in refrigerator. Soup keeps nicely for at least a week.