1. Preheat oven to 400 degrees Fahrenheit. Prepare a roasting pan by coating it lightly with oil. Place all vegetables in the roasting pan. Mix the oyster sauce and maple syrup in a small bowl. Pour over the vegetables. Toss gently to coat the veggies. 2. Place in the oven and bake for 10 minutes. Don't let the vegetables get burned. Remove the roasting pan from the oven and turn the vegetables over. Return to the oven for another 5 minutes.