In a medium bowl, whisk together the ranch dressing, chipotle adobo sauce, and ground cumin. Add the cut chicken pieces, toss to coat thoroughly, and marinate in the refrigerator for at least 15 minutes, or up to 4 hours.

Heat the vegetable oil in a large skillet or grill pan over medium-high heat. Add the marinated chicken (reserving any extra marinade) and cook for 5-7 minutes, turning occasionally, until the chicken is fully cooked through and slightly charred.

While the chicken cooks, gently warm the black beans, corn, and rice in a small pot or microwave until heated through. Set aside.

Warm the flour tortillas individually either on a dry skillet for about 30 seconds per side, or briefly in the microwave, to make them pliable for rolling.

Assemble the burritos: Lay a warm tortilla flat. Layer ingredients down the center: start with a line of rice and beans, top with grilled chipotle chicken, then sprinkle with shredded cheese, diced red onion, and fresh cilantro.

Fold the sides of the tortilla inward over the filling, then tightly roll the bottom edge up and over the filling, continuing to roll until the burrito is securely wrapped. Slice in half and serve immediately.