In a medium mixing bowl, combine the cooked cubed chicken, black beans, corn, chopped red bell pepper, sliced green onions, chopped jalapeños, and chopped spinach.
Add the chili powder, cumin, garlic powder, salt, black pepper, and shredded Monterey Jack cheese to the bowl and mix until evenly combined.
Place an egg roll wrapper on a clean surface in a diamond orientation. Spoon about 2 tablespoons of the filling into the center of the wrapper.
Moisten the edges of the wrapper with a little water, fold the bottom edge up over the filling, fold in the sides tightly, then roll closed to seal. Repeat with remaining wrappers and filling.
Pour oil into a large skillet to about 1 inch deep and heat over medium-high until hot. Fry the egg rolls in batches for about 1–2 minutes per side until golden brown and crispy.
Transfer cooked egg rolls to a paper-towel-lined plate to drain briefly, then serve hot with cilantro ranch dressing.