Preheat oven to 375°F. Line baking sheet with a silicone baking mat and set aside.
Toss onions and peppers in oil and spices and distribute on baking sheet. Roast for 20 minutes, until edges get crispy and veggies are soft to fork.
While the veggies are roasting, set up the rest of your ingredients to build your fajita bowls. Cook quinoa, according to package instructions, drain and rinse canned black beans well.
To assemble your bowls, add shredded lettuce, quinoa, and black beans as the base of your bowl. Add hot veggies on top, along with salsa, avocado or guacamole, and shredded cheese (if desired). Enjoy!