Step 1Preheat oven to 190 °C/ 375 °F (fan assisted), or 210 °C/ 410 °F (conventional). Cut the zucchini and eggplant into small (about 1 cm/ 1/2 inch) slices. Slice the bell peppers. Slice the broccoli and cauliflower (about 1 cm/ 1/2 inch pieces). Halve the red onion and slice the onion. Place all of the vegetables in a large baking tray and top with asparagus spears (snap the hard ends if they are not trimmed).