Preheat oven to 180 (350 degreesf ).
Flatten the chicken to 1/4-inch thickness.
In a medium bowl, combine the pepper jack cheese, spinach, salt and pepper.
Combine the Cajun seasoning and breadcrumbs together in a small bowl.
Spoon about 1/4 c of the spinach mixture onto each chicken breast. Roll each chicken breast tightly and fasten the seams with several toothpicks. This part requires a tiny bit of skill and I typically use about 8 toothpicks in each roll to ensure none of the filling seeps out. Be sure to count how many total toothpicks were used!
Brush each chicken breast with the olive oil. Sprinkle the Cajun seasoning mixture evenly over all. Sprinkle any remaining spinach and cheese on top of chicken (optional).
Place the chicken seam-side up onto a tin foil-lined baking sheet (for easy cleanup). Bake for 35 to 40 minutes, or until chicken is cooked through.
Remove the toothpicks before serving. Count to make sure you have removed every last toothpick. Serve whole or slice into medallians