Pat the chicken breast dry and coat it with the chili powder, cumin, smoked paprika, garlic powder, salt, and cayenne. Heat the olive oil in a skillet over medium-high heat and sear the chicken for 6 to 7 minutes per side until it reaches 165°F (74°C) internally. Rest for 5 minutes, then dice into small pieces.

Return the skillet to medium heat and add the black beans, corn, chopped spinach, and roasted red peppers. Cook for 2 to 3 minutes until the spinach wilts. Take off the heat, fold in the diced chicken and Monterey Jack cheese, then spread the filling onto a plate and cool for 10 minutes.

Mash the avocado in a small bowl, then stir in the sour cream, lime juice, buttermilk, and ranch seasoning until smooth and creamy. Cover with plastic wrap pressed against the surface and set aside.

Place a wrapper in a diamond orientation and spoon about 3 tbsp of filling across the center. Fold the bottom corner up, fold in the sides, then roll forward and seal the top corner with a dab of water. Repeat with all 10 wrappers.

Heat vegetable oil in a heavy pot to 350°F (175°C) with about 2 inches of depth. Fry the egg rolls in batches of 3 to 4 for 5 to 6 minutes per batch, turning every 2 minutes, until deep golden brown. Drain on a wire rack.

Cut each egg roll on the diagonal and arrange cut side up on a serving board. Spoon the avocado ranch into a small bowl alongside, or drizzle it across the tops.