Preheat the oven to 425°F (220°C).
Arrange the sausages in a roasting tin or casserole dish with the sweet potatoes, carrots, red onions and garlic, making sure not to overload the tin.
In a measuring jug or bowl, mix together the chicken stock, mustard powder, honey and oregano.
Pour the stock mixture over the sausages and vegetables, tossing to make sure everything is coated with the stock.
Season with salt (adjust according to how salty your stock is) and pepper and toss again.
Scatter over the sage leaves.
Roast in the oven for 45 to 55 minutes.
Serve straight from the roasting tin, making sure to spoon over any remaining juices.
