Pre-heat oven to 350 degrees.
After prepping all veggies, place zucchini on paper towels to drain, adding a sprinkling of salt to help release the moisture. Pat dry with fresh clean paper towel to dry. Coat a medium sized roasting pan with cooking spray. Place all vegetables in roasting pan, coat with olive oil, salt, pepper, rosemary, fennel and thyme. Toss everything until well coated.
Tear or cut sausage into bite size chunks and place on top of veggies. Roast at 350 for 50 minutes.
Remove veggies and sausage from oven. With a spatula, push vegetables into the center of the hot roasting pan- moving them away form the edge. Tuck the thawed puff pastry onto the roasting pan over the veggies, tucking the edges slightly under the vegetable mixture. Like tucking a child into bed. Return to oven and bake another 30 minutes or until dough is golden brown and puffy.
After pastry is golden brown, remove from oven. Loosen the veggies once again with a spatula to prevent sticking. While still hot, using a thick towel, invert the roasting pan onto a serving platter- carefully. Tear the mozzarella into pieces and drop onto hot veggies. Drizzle with balsamic vinegar. Slice and serve immediately.