In a bowl, combine the prosciutto, spinach, and cheese.
Pound out chicken thighs, skin side down, to an even thickness; about 1/4 inch to 1/2 inch.
Sprinkle Italian Seasoning over chicken.
Use 1/6 of the amount of prosciutto filling and place it in the center of each thigh. Roll up the thighs and season skin with salt and pepper.
In a large oven-safe sauté pan or cast iron skillet, heat the oil over high heat. Place each thigh in the pan with skin side up. After about 2 minutes, flip over with skin side down for an additional 2 minutes. Lower heat to medium and cook for 12 minutes to render the fat.
Flip chicken over one last time, with skin facing up, and place in preheated oven for an additional 5 minutes.