Prepare quinoa according to packaging.
Preheat oven to 375 degrees and line a large rimmed baking sheet with parchment paper.
In a large bowl, toss together next 12 ingredients (squash through red pepper flakes). Make sure everything is evenly coated, then transfer to baking sheet. Place in oven and roast for 35 to 45 minutes or until veggies are fork tender.
While veggies cook, prepare tahini sauce. In a small bowl, whisk together all ingredients for sauce except water. Once mixed well, slowly add water to get desired consistency. Should still be somewhat thick, but thin enough to drizzle.
Once veggies are done, remove from oven and serve on top of quinoa with drizzle of tahini sauce.