Preheat the oven to 200°C. Cut the pumpkin, onion, and apple into pieces and mix them in a bowl with salt, pepper, oil, and cumin. Spread the mixture on a lined baking sheet and bake for about 20 minutes. Peel the potatoes and cook them until tender, about 20 minutes. Drain the potatoes, dry them, and mash them. Meanwhile, heat the milk in a saucepan and add it to the mashed potatoes. Cut the cheese into cubes. Next, add the pumpkin mixture, cheese, cinnamon, and parsley to the mashed potatoes and mix well. Season to taste with salt and pepper.