Preheat oven to 375°F.
On a large sheet pan (optionally covered with parchment paper), toss the carrots with 2 tablespoons of the olive oil, honey and harissa. Lightly season with salt and freshly ground black pepper. Place pan in oven and roast until carrots are just fork tender. Remove from the oven. Set aside.
In a small bowl, combine the yogurt, tahini and half of the lemon juice. Taste for seasoning and adjust as needed. Set aside.
Place the spinach in a medium bowl. Drizzle with 1 tablespoon of the olive oil and half of the lemon juice, seasoning with salt and pepper. Gently toss the spinach to lightly dress with the olive oil and juice. Transfer spinach to a platter.
Lay the carrots across the top of the spinach. Spoon the yogurt mixture over the carrots. Sprinkle with the toasted seeds. Serve hot, warm or at room temperature.