Preheat your oven to 425°F and toss sweet potatoes, parsnips, and red onion with 2 tablespoons of olive oil and 1 teaspoon of salt. Spread evenly on baking sheets and roast for 15 minutes. Toss the vegetables, rotate the pans, and roast for another 10 minutes until tender and golden.
Bring 2 cups of water and 1/2 teaspoon salt to a boil in a saucepan. Stir in the rinsed quinoa and cinnamon, reduce heat to low, cover, and simmer for 15 minutes. Remove from heat, let sit covered for 5 minutes, then fluff with a fork.
Combine remaining olive oil, apple cider vinegar, maple syrup, Dijon mustard, and salt in a jar. Seal tightly and shake well until the dressing is fully emulsified and slightly thickened.
In a large bowl, toss the warm roasted vegetables, quinoa, thyme, and sage with the dressing. Add apple pieces and pepitas just before serving to maintain their crunch. Serve warm or at room temperature.