Preheat the oven to 400°F.
Chop the carrot, red bell pepper, and onion into small cubes. Toss them with olive oil, dried thyme, salt, and pepper.
Spread the vegetables on a baking sheet and roast in the oven for about 15-20 minutes until tender and lightly caramelized.
While the vegetables roast, heat a skillet over medium heat. Add the lean ground beef and cook until browned, breaking it apart with a spatula.
Stir in the tomato paste and lightly simmer the beef for 2-3 minutes. Once roasted, mix the vegetables into the beef, combining well.
For the mash, pierce the sweet potato with a fork and microwave on high for about 5-6 minutes or until soft, or alternatively bake until tender.
Scoop out the sweet potato flesh into a bowl, add low-fat milk, and mash until smooth. Season with a pinch of salt and pepper.
Assemble the dish by placing the beef and roasted vegetable mixture in a serving dish and topping it with a generous layer of creamy sweet potato mash.
Serve warm and enjoy this hearty, balanced meal.