Preheat the oven: Set to 400 °F (ca. 204 °C). Line two large baking sheets (approx. 37×25×2.5 cm) with foil.
Prepare the herb mix: In a small bowl, combine parsley, rosemary, oregano, basil, 1/4 tsp salt, and 1/4 tsp ground pepper.
Season the chicken: Place the chicken pieces on one baking sheet and sprinkle with half the herb mixture.
Prep the vegetables: In a large bowl, toss mushrooms, onion, bell pepper, and garlic with olive oil. Spread them out on the second baking sheet.
Bake the chicken and vegetables: Roast both sheets in the oven for about 30 minutes. Stir mushrooms once midway. Remove chicken when cooked through and cover to keep warm.
Add remaining vegetables: To the mushroom tray, add asparagus (or green beans), cherry tomatoes, white beans, olives, balsamic vinegar, and the remaining herb mix. Toss well and roast for another 15 minutes.
Serve: Slice the chicken into smaller pieces and serve over the roasted vegetables. Garnish with additional herbs if desired.