How to Make It
Preheat oven to 400°F. Toss together squash, daikon, oil, 1 teaspoon salt, and pepper in a large bowl. Arrange squash mixture in a roasting pan in a single layer.
Process kombu in a spice grinder until finely ground, about 25 seconds. Stir together 1 teaspoon ground kombu (reserve any remaining for another use), butter, garlic, lemon zest, and 1 3/4 teaspoons salt until thoroughly blended. Carefully run your fingers underneath skin of chicken breasts and thighs to loosen. Spread butter mixture under skin. Season outside of chicken with remaining 1 teaspoon salt. Place chicken on top of squash mixture.
Roast in preheated oven until a thermometer inserted into thickest portion of breast registers 155°F, about 1 hour, gently stirring squash mixture halfway through. Remove pan from oven; let chicken rest at least 15 minutes. Carve chicken, and serve with roasted vegetables.