Trim tough outer leaves from fennel. Cut fennel bulbs in half crosswise; discard cores. Cut into 1/2-inch-thick pieces. Place fennel pieces in a large roasting pan. Coat fennel with cooking spray. Add 1 tablespoon oil, 1/2 teaspoon salt, and 1/4 teaspoon pepper; toss to coat. Bake at 425° for 20 minutes. Stir fennel; bake an additional 10 minutes or until tender.
Cook pasta according to package directions, omitting salt and fat. Drain, reserving 2 tablespoons pasta cooking water. Return pasta to pan. Add reserved pasta cooking water, fennel, remaining 1 tablespoon oil, remaining 1/2 teaspoon salt, remaining 1/4 teaspoon pepper, feta, and remaining ingredients; toss well.