Place all the ingredients (except the vegetable stock) in a resealable freezer bag. Seal the bag, then shake well to coat everything in oil. Alternatively, you can put everything in a large bowl and stir the ingredients until they are fully coated in oil.
Pour into a large roasting tin, spreading the ingredients out into one even layer, ensuring that the sausages aren’t covered by any of the vegetables. Season well with salt and pepper. Roast for about 30–35 minutes until golden brown.
Remove from the oven, turn the sausages over and toss the vegetables in the cooking juices.
Pour in the stock and return to the oven for another 20 minutes at a medium-high heat until browned and the sausages and potatoes are cooked and tender.