Preheat your oven to 400°F (200°C).
Prepare the vegetables: peel and dice the sweet potato, carrot, parsnip, and onion into even bite-sized pieces.
Lightly toss the diced sweet potato, carrot, and parsnip with half the olive oil, salt, and pepper, and spread them on a baking sheet.
Roast the vegetables in the preheated oven for about 20-25 minutes, or until tender and slightly caramelized.
While the vegetables roast, heat a skillet over medium heat and add the remaining olive oil.
Add the diced onion and sauté until translucent, about 3-4 minutes.
Stir in the lamb mince, breaking it up with a spatula, and cook until browned and cooked through, around 7-8 minutes. Season with salt, pepper, and any additional herbs you prefer.
Once the vegetables are roasted, gently fold them into the skillet with the lamb. Mix well to combine the flavors.
Adjust the seasoning if needed, and serve warm.