Peel, trim and rough-chop all the vegetables and place in a large roasting tin with a good drizzle of olive oil.
Add the herbs.
Toss the vegetables in the oil to coat and then add the black pepper and salt. Toss again.
Roast in the oven for about an hour, stirring occasionally to prevent the edges burning.
Slow-Cook with Water
When the vegetables are roasted, remove from the oven and place in a slow cooker (or very large saucepan).
Add an extra good grind of salt.
Add enough water to cover the vegetables by about 4 to 5 cm (1½ to 2 inches).
Slow-cook on maximum for about 3 hours (or slight simmer on the hob for 2 to 3 hours).
When cooked, allow to cool.
Use a sieve to drain and separate the liquid (vegetable stock) into a large jug/soup storage container and set aside. Save the vegetables into a separate storage container (topped up with a little water) to liquidise later and make vegetable soup.