Preheat the oven to 180 °C (350 °F), conventional oven (top and bottom heat).
Clean 1 kg mixed vegetables and cut into bite-size pieces.
In a bowl, season the vegetable pieces with salt, pepper and garlic if using, and toss with 3 tbsp olive oil.
Spread the seasoned vegetables on a baking sheet lined with parchment paper and roast in the oven for about 15 min.
Toast the 2 tbsp pumpkin seeds and set aside.
Meanwhile, make a marinade in a blender from 2 tbsp coarse Dijon mustard, 2 tbsp honey, the leaves of 4 sprigs marjoram and 2 sprigs rosemary as well as 40 ml white balsamic vinegar, 100 ml olive oil and, if you like, some grated orange zest.
Toss the finished vegetables with the marinade in a bowl while still warm.
Clean 1 head radicchio, cut into pieces and add to the vegetables shortly before serving.
Garnish with the pumpkin seeds.