Line a baking sheet with a sheet of parchment paper, then preheat the oven to 375°F. Place cubed butternut on a baking sheet and cover with 1 tablespoon of oil and a sprinkle salt. Bake for 45 minutes, or until squash is tender and slightly browned.
Line a second sheet with parchment paper. Cut the tomato and shallots in half and place them on a baking sheet. Cover with oil and salt and bake for 10 minutes.
Remove tomatoes and roast onions for additional 15 minutes.
While the vegetables are cooking, prepare the quinoa. Rinse quinoa and place in a medium saucepan with 1 to 1/2 cups of water and 1 teaspoon of salt. Bring to a boil, then turn down the heat to simmer until most of the liquid has been absorbed, about 15 to 20 minutes. Fluff with a fork.
Place quinoa and mixed greens in a large bowl. Mix with a salad dressing and transfer to a serving dish. Layer roasted vegetables, and top with sliced avocado.