Roasted Vegetable Soup - cooking recipe

Ingredients

2 onions, cut into 1-inch dice
2 carrots, peeled and cut into 1-inch lengths
2 celery ribs, sliced 1/2 inch thick
1 medium turnip, peeled and cut into 1-inch dice
1/2 red bell pepper, cut into 1-inch squares
1 small sweet potato, peeled and cut into 1-inch dice
8 white mushrooms, cleaned and quartered
4 large garlic cloves, whole and unpeeled
2 tablespoons extra-virgin olive oil
6 cups vegetable broth, divided
15 ounces diced tomatoes, preferably fire roasted, with their juice
1 teaspoon kosher salt
1/2 teaspoon ground black pepper
1/2 teaspoon dried rosemary, crushed
1/2 teaspoon dried thyme
2 tablespoons chopped fresh parsley
3 tablespoons couscous, preferably whole wheat

Preparation

Preheat an oven to 425 degrees F. Toss the onions, carrots, celery, turnip, bell pepper, sweet potato, mushrooms, and garlic with olive oil on a large rimmed sheet pan. Spread out into an even layer and roast for 30 minutes, or until the vegetables are tender and lightly browned at the edges.
Scrape the vegetables into a 5- to 6-quart slow cooker. Pour 1 cup of the vegetable broth onto the sheet pan and scrape up any browned bits clinging to it; scrape into the cooker. Add the remaining 5 cups broth, the diced tomatoes and their liquid, salt, pepper, rosemary, and thyme, cover the cooker and cook for 2 to 3 hours on high, or 4 to 6 hours on low, until the flavors are blended.
Stir in the couscous and parsley and cook for 5 minutes more.