Heat the Oven: Heat the oven to 400° F and place the rack in the middle of the oven. Line a baking sheet with parchment paper or tin foil and spray with non-stick spray.
Make the Ginger-Scallion Sauce: In a small bowl, whisk together the ginger-scallion sauce ingredients until combined. Set aside.
Roast the Veggies: In a medium bowl, toss the vegetables in the sesame oil and season with salt and pepper. Toss to coat. Transfer the vegetables to the baking sheet, arranging them in a single layer. Roast the vegetables, stirring every 10 minutes or so, for approximately 45 minutes until tender and cooked through. This may take more or less time depending on your oven. Remove from the oven and set aside.
Make the Quinoa: While the vegetables are cooking, combine the quinoa, 1 teaspoon of sesame oil, and water in a medium saucepan. Bring to a boil over medium-high heat, and then cover and simmer for approximately 15 minutes until the quinoa is cooked through.
Toss it Together! In a large bowl, combine the vegetables and quinoa. Toss with the ginger-scallion dressing. While the mixture is still warm, stir in the spinach, and toasted sesame seeds. Cover tightly with plastic wrap or transfer to an airtight container and refrigerate for at least an hour before serving. Toss in the cilantro to garnish.