Preheat your oven to 400F and line two baking sheets with parchment or foil. Place the squash and grapes on one tray and drizzle them with a tablespoon of the oil. Place the Brussels on the other sheet and drizzle them with the remaining tablespoon oil. Sprinkle the vegetables with salt and pepper. Transfer both sheets to the oven and roast for 25-35 minutes, or until they squash is very tender and the sprouts are tender and crisping on the outside. Check the vegetables at 25 minutes. If your Brussels sprouts are getting too crispy but the squash needs more time, you can remove the sprouts from the oven first.
While the vegetables roast, rinse the quinoa through a fine sieve. Bring 1 1/2 cups water to a rolling boil in a sauce pot. Add the quinoa to the water, cover, and reduce the heat to low. Simmer the quinoa for 13 minutes, then remove the pot from heat. Let the pot stand for five minutes, then fluff the quinoa grains with a fork. Cover the pot again and let the quinoa steam while you finish the remaining steps for the salad.
To prepare the dressing, whisk all ingredients together in a small mixing bowl or shake them up in a sealed mason jar.
When the roasted vegetables are ready, allow them to cool until they're slightly warm or room temperature. Toss the vegetables, cooked quinoa, greens, and dressing together. Taste the salad and adjust the vinegar, salt, and pepper as desired. Serve.
Notes
Leftover salad will keep in a sealed container in the fridge overnight.