Preheat oven to 450 degrees Fahrenheit and line two baking sheets with Gefen Parchment Paper.

Toss sweet potato and potatoes with 1/4 cup oil and 1/2 teaspoon salt and spread on one baking sheet. Toss squash, zucchini and onions with remaining 1/4 cup oil and 1/2 teaspoon salt on the second baking sheet. Roast for 45 to 60 minutes or until golden brown and tender.

Spread lettuce on a large platter and add roasted vegetables. Top with toasted walnuts and radishes.

Combine oil, lemon juice, salt, and pepper in a glass jar. Close tightly and shake vigorously for about 10 seconds or until fully combined.

Let stand for 30 minutes at room temperature to let the flavors meld. Shake and pour over salad immediately before serving.