Pre-heat the oven to 425 degrees F. Place the delicata squash slices on a rimmed baking sheet. Toss the squash with 2 tablespoon of the olive oil, 1 teaspoon of cumin, salt and pepper. Roast for 15 minutes.

Combine the remaining 1/2 teaspoon of cumin, 1 tablespoon of olive oil and the scallions in a small bowl. Season with salt and pepper and toss. Scatter this scallion mixture over the squash and continue to roast squash until tender, about 10 minutes longer.

Whisk the lemon juice, tahini and 1 tablespoon of water in a small bowl to blend. Gradually whisk in remaining 2 tablespoons of the olive oil. Season with salt and pepper. Transfer the squash to a platter. Drizzle the tahini sauce over the squash, or serve on the side for dipping. Sprinkle the red pepper flakes over the squash.