|Preheat oven to 500°F.|
|Toss cauliflower, squash and onion in a large bowl with oil, garlic powder, 1/2 teaspoon pepper and salt. Spread on a rimmed baking sheet. Roast, stirring once, until tender and browned in spots, 25 to 30 minutes.|
|Meanwhile, combine broth and water in a small saucepan. Bring to a boil.|
|Slowly whisk in cornmeal, rosemary and the remaining 1/4 teaspoon pepper until smooth. Reduce heat to low, cover and cook, stirring occasionally, until very thick and creamy, 10 to 15 minutes. Stir in cheese; remove the polenta from the heat.|
|Serve the vegetables over the polenta.|
Tip: To prepare florets from a whole head of cauliflower, remove outer leaves. Slice off the thick stem. With the head upside down and holding a knife at a 45° angle, slice into the smaller stems with a circular motion—removing a “plug” from the center of the head. Break or cut florets into the desired size. To store, refrigerate in a plastic bag for up to 5 days.