Preheat your oven to 375°F (190°C).
In a mixing bowl, combine lean ground turkey, rolled oats, egg white, diced carrot, parsnip, onion, and minced garlic. Season with salt, pepper, and dried thyme.
Gently mix the ingredients until just combined, being careful not to overwork the meat.
Shape the mixture into a small loaf and place it on a lightly greased baking dish.
Bake the meatloaf in the preheated oven for about 25-30 minutes, or until the internal temperature reaches 165°F.
While the meatloaf is baking, prepare the roasted root vegetables. Spread additional diced carrots, parsnips, and onions on a baking sheet, drizzle with a small amount of olive oil (optional), season with salt and pepper, and roast in the oven for about 20 minutes.
For the creamy mushroom gravy, heat a small pan over medium heat. Add the sliced mushrooms and sauté until tender, then stir in the low-fat milk. Allow the mixture to simmer for a few minutes until slightly thickened, seasoning with salt and pepper as needed.
Once cooked, slice the turkey meatloaf and serve it with a generous spoonful of the mushroom gravy alongside the roasted root vegetables.