Cut the Roasted Winter Vegetables into 1/2-inch pieces. Heat the olive oil in a medium Dutch oven over medium heat. Add the roasted vegetables and cook for 2 to 3 minutes to heat through. Add the vegetable stock, escarole, navy beans, Parmesan rind and 4 cups water, and bring to a boil. Reduce the heat to a simmer and cook for 30 minutes to melt the Parmesan into the soup and combine the flavors. Season to taste with salt. Remove and discard the Parmesan rind.
Right before serving, stir in the thyme and lemon zest.
Roasted Winter Vegetables:
Preheat the oven to 425 degrees F.
In a large bowl, toss the carrots, parsnips, beets and radishes together with the thyme, garlic, olive oil, nutmeg, 1 teaspoon salt, and pepper to taste.
Arrange the vegetables in one layer on a rimmed baking sheet. Roast until tender and golden brown in places, stirring once, about 25 minutes. Stir in the lemon zest, then transfer to a serving bowl.