Preheat oven to 425.
Cut the fennel bulbs into wedges (around 8 wedges per bulb).
In a small bowl, combine olive oil, garlic, vinegar, mustard, thyme, salt, and pepper, and mix together well.
Blend 2 TBSP of the parmesan cheese into the oil mixture.
In a large bowl, toss the fennel with the oil mixture.
Place the fennel on a baking sheet coated with cooking spray. Sprinkle the remaining 1 TBSP of parmesan cheese over top the wedges.
Roast until the fennel pieces are tender and browned, 30-40 minutes.