Preheat the oven to 425º F.
In a large bowl, place the cut green beans, broccoli, mushrooms, Brussels sprouts, carrots, onion, garlic and olive oil. Toss the vegetables together until they are fully coated.
Divide the mixture between two greased 15x10-inch pans or a large 18x26-inch baking sheet.
Place the baking sheets into the oven and roast for 20 to 25 minutes or until the vegetables are fork tender.
Remove the pans from the oven and transfer the medley to a large bowl.
Add the remaining ingredients and toss together.
