Start by preheating your oven to 425°F (220°C). This temperature is ideal for roasting vegetables, allowing them to cook through while developing that enticing golden-brown exterior.

While the oven heats up, wash your zucchini and squash thoroughly. Slice them into half-inch rounds. Uniformity is key here, as consistent sizes ensure even cooking.

In a large bowl, combine your olive oil, sea salt, black pepper, onion powder, mixed Italian herbs, and red pepper flakes. Toss your sliced vegetables in this flavorful mixture. Make sure every piece is coated; this ensures an even distribution of flavors.

Take a baking sheet and line it with parchment paper or lightly grease it. Spread the seasoned zucchini and squash in a single layer. Avoid overcrowding, as that can lead to steaming rather than roasting. Each round needs some personal space to develop that delightful caramelization.

Place your baking sheet in the oven and roast for about 20-25 minutes. Halfway through, flip the vegetables to ensure even cooking. You've got to keep an eye on them; the goal is tender insides with beautifully browned edges.

Once roasted, take the sheet out and drizzle with fresh lemon juice. This brightens up the dish significantly. Give them a gentle toss and let them rest for a few minutes before serving.