In a large bowl, whisk together grapeseed oil, salt and pepper, to taste. Add the squash, carrots, onions, garlic and potatoes, tossing to coat. Put the coated vegetables on a sheet pan, and roast until the onions are translucent, about 20 to 25 minutes.
Meanwhile, in large stock pot, over medium heat add the stock, beans, bay leaf, thyme, and cook for 10 minutes, stirring occasionally. With a hand blender pulse stock and bean mixture until the beans are slightly pureed. Remove the vegetables from oven and add to pot, then stir in the broccoli and tomatoes. Cook until all the vegetables are cooked through, about 30 to 35 minutes.
For a thicker soup, a cornstarch and water mixture or a light roux can be blended in to thicken the consistency.