For the veal must roast, first clean and coarsely chop the root vegetables. Peel and coarsely dice the onions. Preheat the oven to 150 °C.
Rub the meat thoroughly with mustard, salt and pepper. In a large frying pan, brown on all sides in a little oil. Lift out, place in a roasting pan and pour the must over it. Place in oven for about 1 to 1 1/2 hours, basting repeatedly with must.
Sauté onions and vegetables in the same pan and add a little must to soften. Season with salt and pepper.
Remove the shoulder cut from the oven and let it rest, wrapped in aluminum foil. Meanwhile, empty the gravy through a sieve into a pot and let it boil down or thicken a little.
Serve the veal roast with the root vegetables.