Make the vegetables: Preheat oven to 450 degrees. Toss all of the ingredients on a rimmed baking sheet, and spread in a single layer. Roast, stirring once, until sweet potato wedges are golden and tender, about 25 minutes. Let cool on baking sheet.
Make the dressing and salad: Whisk lime juice, oil, and parsley in a large bowl. Season with salt and pepper. Stir in roasted vegetables and turkey. Toss with watercress, radishes, and half of the cheese. Sprinkle remaining cheese on top, and serve immediately.