Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Pat the turkey breast dry and rub with 1 tablespoon of olive oil, oregano, thyme, half of the salt, half of the pepper, and the garlic powder.
Peel and dice the sweet potatoes into 1-inch cubes, toss them with 0.5 tablespoons of olive oil and the remaining salt and pepper, then place them on the baking sheet with the turkey.
Roast the turkey and sweet potatoes for 20 minutes.
Toss the broccoli florets with the remaining 0.5 tablespoon of olive oil and add them to the baking sheet, roasting everything for another 15-20 minutes until the turkey reaches an internal temperature of 165°F.
While the meal roasts, whisk together the Greek yogurt, lemon juice, and chopped fresh dill in a small bowl to create the sauce.
Slice the roasted turkey and serve it alongside the sweet potatoes and broccoli, topped with the yogurt sauce, fresh avocado slices, and crushed walnuts.