Heat the oven to 450°F. Place tomato halves cut-side up on a rimmed sheet, brush with 1 tablespoon oil and season with 1/2 teaspoon salt and pepper. Roast for 25 to 30 minutes until softened with browned edges, then chop coarsely, saving the juices.
Meanwhile, heat remaining oil in a soup pot over medium heat. Cook ground turkey and onion for 8 to 10 minutes, breaking turkey into small crumbles, until turkey reaches 165°F. Stir in garlic for 30 seconds.
Add turnips, carrots, broth, thyme and remaining salt. Bring to a simmer and cook for 8 minutes.
Add cauliflower and chopped roasted tomatoes with their juices. Simmer for 10 to 12 minutes until turnips, carrots and cauliflower are tender.
Stir in spinach and cook for 2 minutes until wilted. Remove from the heat, stir in vinegar and divide among 6 bowls.