Peel onions and cut 300 g into strips. Peel garlic cloves and dice finely. Season meat from both sides with salt and pepper. Spread mustard on the sliced side, sprinkle evenly with paprika, spread strips of onion and garlic on top.
Roll up the roast from the cross side and tie up with kitchen string. Place in a flat roasting pan or on a greased fat pan and cook in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 2 hours
Cover the roast with aluminium foil for the last 1/2 hour, depending on the degree of browning. Halve the remaining onions and garlic bulb. Peel and clean the carrots, cut them in half lengthwise and cut them into pieces of about 4 cm length.
Wash and clean the celery and cut into 4 cm long pieces. Wash herbs, shake dry. 45 minutes before the end of the cooking time, spread vegetables and herbs around the roast, except for something to garnish.
Sprinkle with oil and season with salt. Remove the roast, cut into slices and serve hot with the vegetables.