Preheat the oven to 200°C (390°F).

Peel and chop the sweet potatoes, red onions, and carrots. Toss them in olive oil, season with salt and pepper, and roast for 25-30 minutes until tender and slightly caramelized.

While the vegetables are roasting, peel and chop the potatoes for the mash. Boil them in salted water for 12-15 minutes until soft.

Drain the potatoes and mash them with butter and milk until smooth and creamy. Season with salt and pepper to taste.

Cook the vegetarian sausages according to the package instructions (pan-fry or bake for 10-12 minutes until heated through).

Serve the vegetarian sausages with a side of mashed potatoes and roasted vegetables.