Winter squashes are grown during the summer. They are called winter squash because they have a hard skin that keeps the squash fresher through the winter months after harvest. Their flavor is on the sweet side when roasted. Peeling raw winter squashes is a challenge. Scrape the flesh off the peel after they've been roasted. Summer squash including patty pan, yellow crookneck and zucchini don't benefit as much from oven-roasting.
Root vegetables, with the exception of radishes, are ideal for oven-roasting roasting. While radishes can be cooked, they're most familiar raw in salads. Carrots and beets become even sweeter when they are oven-roasted. Scrub root vegetables to remove grit and slice off the tops. Neither carrots nor beets must be peeled -- the skins slip off beets after roasting. Other root vegetables to oven-roast include turnips, parsnips and rutabagas.
Cabbage leaves don't roast well, but quartered whole cabbages do. The high heat of oven-roasting dries out individual cabbage leaves and turns them crispy. When the cabbage is roasted in quarters, the leaves become soft and the flavor mellow. Brussels sprouts are also good candidates for oven-roasting. Remove any excess stem and wilted leaves. Broccoli and cauliflower roast better at a lower temperature, no more than 350 degrees Fahrenheit, for less time than other vegetables.
White potatoes, sweet potatoes and yams turn a vegetable roast side dish into a satisfying vegetarian entrée. Scrub the potatoes well before oven-roasting. If the potatoes vary in size, cut them into equal chunks so they all are ready at the same time.
White, yellow, and red onions turn sweet and soft when oven-roasted, losing the familiar onion bite. Leeks must be cut in half lengthwise and rinsed well. Dirt often gets trapped between the layers. Only roast the white and light green parts -- the dark green leaves won't soften. Scallions usually roast too quickly and turn brown. Add them about 10 minutes before the roasting time is done for the rest of the vegetables.
Warm Season Vegetables
Most of the warm season vegetables such as tomatoes and green peppers roast quickly. Tomatoes will turn to mush if they are oven-roasted too long. Oven-roasting brings out the flavor of corn -- brush with olive oil before roasting. Add a squirt of lime juice after the corn has roasted and sprinkle with cayenne flakes.