Heat the oven to 400°F. Lightly grease a 12-cup muffin tin. Line a rimmed baking sheet with parchment paper.
Put the carrots, parsnips, and sweet potato on the baking sheet. Toss them with 1 tablespoon of olive oil and half of the salt and pepper. Spread them into an even layer.
Roast the vegetables for 15 minutes. Meanwhile, gently squeeze excess liquid from the grated apple and place it in a mixing bowl with the ground turkey, egg, breadcrumbs, milk, sage, and remaining salt and pepper. Mix just until combined.
Divide the turkey mixture among 8 muffin cups, filling each about three-quarters full. Brush the tops with the remaining olive oil.
Remove the baking sheet from the oven and turn the vegetables. Return the vegetables and muffin tin to the oven. Bake for 18 to 22 minutes, until the vegetables are tender and the turkey muffins reach 165°F in the center.
Let the muffins rest in the tin for 5 minutes. Serve them with the roasted root vegetables.