Preheat the oven to 425°. In a large mixing bowl add in the broccoli, fennel, onion, pesto, olive oil, salt and pepper and toss together. Before placing your vegetables on the sheet pan, line it with tin foil and spray with a non-stick cooking spray for easy cleanup.
Make sure the sheet is large enough to hold the vegetables in a single layer so they receive an even bake. Roast for 25 to 35 minutes, until crisp-tender and the tips of some of the florets are lightly browned. Garnish with pine nuts.