Wash the asparagus and cut off the woody ends. Peel and wash the rest of the vegetables and potatoes. Cut all vegetables and potatoes into finger-thick pieces of equal width (approx. 2 x 5 cm).
Place in an ovenproof dish.
Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Melt butter. Mix with oil and approx. 1⁄2 tsp. salt and pepper. Pour over vegetables and massage in well with hands.
Close the tin with aluminium foil and bake in a hot oven for about 20 minutes. Then remove the foil and continue baking for 10-15 minutes until the vegetables are soft.
Wash herbs, shake dry. Coarsely chop rosemary needles and thyme leaves. Sprinkle over vegetables. Season to taste with sea salt. Serve with chili dip and mustard oil.