Preheat oven to 375º and line two baking sheets with parchment paper.
In a small bowl, combine salt, paprika, pepper, chipotle, cumin, cayenne, and garlic powder. Stir together.
Spread sweet potatoes on sheet pan and drizzle with 2 Tablespoons of oil. Sprinkle half of the seasoning over them and mix them up to coat evenly.
On the second sheet pan, spread bell peppers and onion. Drizzle with remaining oil and sprinkle the other half of the seasoning. Mix to coat evenly.
Place the sweet potatoes into the oven and bake for 10 minutes. Then place the bell pepper + onion sheet pan into the oven and continue baking for 30 minutes. Remove both pans at the halfway mark to stir for even baking.
While the veggies are baking, you have just enough time to make your brown rice or quinoa or other grain of choice!