Preheat oven to 425 degrees Fahrenheit. Line two baking sheets with Gefen Parchment Paper.

In a bowl, toss the sweet potatoes, butternut squash, yellow squash, carrots, and garlic with 1/2 cup olive oil, garlic powder, salt, and pepper.

Spread the vegetables on the baking sheets in a single layer and roast for 45 minutes.

In a seven-quart pot, heat the remaining 1/4 cup olive oil over high heat. Add the leeks and onions, and sauté for 15 minutes. Reduce heat to low and continue sautéing until the vegetables in the oven are finished roasting.

Add roasted vegetables and water to the pot. Use an immersion blender to purée until smooth.