Preheat your grill or grill pan over medium-high heat.
In a small bowl, mix together the chili powder, garlic powder, onion powder, smoked paprika, cumin, salt, and pepper. Rub this spice mixture evenly over the chicken breasts.
Drizzle the olive oil over the chicken and let it marinate for about 15 minutes.
Grill the chicken for 6-7 minutes on each side or until the internal temperature reaches 165°F. Remove from the grill and let it rest for 5 minutes before slicing.
In a large bowl, combine the cooked rice, black beans, and half of the chipotle ranch dressing. Mix well.
To assemble the burritos, lay a tortilla flat and add a portion of the rice and bean mixture, sliced grilled chicken, shredded cheese, lettuce, diced tomato, and avocado.
Drizzle the remaining chipotle ranch dressing over the top.
Fold in the sides of the tortilla and roll it up tightly from the bottom to the top. Repeat with the remaining tortillas.
If desired, grill the wrapped burritos for an additional 2-3 minutes on each side to crisp up the tortilla.
Slice in half and garnish with fresh cilantro if using. Serve immediately.