Heat the oven to 400°F. Lightly grease 8 cups of a standard muffin tin.
In a large bowl, combine the ground turkey, grated apple, egg, breadcrumbs, milk, sage, salt, and black pepper. Mix gently until just combined.
Divide the turkey mixture among the 8 prepared muffin cups. Shape each portion lightly so it sits evenly in the cup without packing it down.
Put the carrots, parsnips, and sweet potato on a rimmed baking sheet. Toss them with the olive oil, then spread them out in a single layer.
Place the muffin tin and baking sheet in the oven. Roast for 25 to 30 minutes, turning the vegetables once, until the vegetables are tender and the turkey muffins reach 165°F in the center.
Let the muffins rest for 5 minutes before removing them from the tin. Serve with the roasted root vegetables.