Preheat the oven to 375℉ or about 190℃ - I set my fan oven at 180℃.
Prepare your chosen vegetables. De-seed and cut the peppers into chunks roughly one inch square. Slice each zucchini in half lengthwise and then chop the halves into half moons about a quarter inch thick. Peel the onions and cut them in about eight pieces each. Then cut each piece in half and separate the layers. Peel and cube any root vegetables (sweet potatoes, butternut squash, parsnips, carrots).
If using root vegetables:-Speed whatever combination of sweet potatoes, squash, parsnips and or carrots over one or two baking sheets/sheet pans. Drizzle with some of the oil and pop in the oven for about 15 minutes to give them a head start. After 15 minutes, add any remaining vegetables to the pan along with the chopped cloves of garlic.
Drizzle with the remaining oil, balsamic vinegar (if using) and sprinkle with salt, pepper, and any of the spices you are choosing to use (cumin seeds, chilis etc) except the parsley, which is best sprinkled on when the vegetables have finished cooking. Toss the vegetables together and put back in the oven.
Roast in the oven for about 20 to 25 minutes, turning and mixing half way through, until the vegetables are cooked through and beginning to turn golden on the edges. Cooking time can vary depending on how big you chop your vegetables, so all timings are just a guide.
If you are not using root vegetables:Spread the vegetables over one or two sheet pans/baking sheets. Drizzle with all the oil, balsamic vinegar (if using) and sprinkle with salt, pepper, and any of the spices you are choosing to use (cumin seeds, chilis etc) except the parsley, which is best sprinkled on when the vegetables have finished cooking. Toss the vegetables together and put back in the oven.
Roast in the oven for about 20 to 25 minutes, turning and mixing half way through, until the vegetables are cooked through and beginning to turn golden on the edges.