Heat a large heavy skillet with olive oil and fry fresh sage leaves. Set aside.
Sprinkle the chicken with salt and pepper. Lay 1 slice of prosciutto atop each chicken cutlet.
Squeeze the frozen spinach to remove the excess water. Season the spinach with salt and pepper. In a small bowl, toss the spinach with olive oil.
Arrange an even, thin layer of spinach atop the prosciutto slices. Sprinkle the Parmesan evenly over each. Roll up each chicken cutlet. Secure with a toothpick.
Heat the remaining 2 tablespoons of oil in your skillet over high heat. Add garlic, the fried sage and the chicken and cook just until golden brown, about 2 minutes per side. Add the chicken broth and lemon juice, and scrape the browned bits off the bottom of the pan with a wooden spoon. Bring the liquid to a boil. Reduce the heat to medium. Cover and simmer until the chicken is just cooked through, about 8 to 10 minutes.
Transfer the chicken to a platter. Simmer the cooking liquid over high heat until it is reduced, about 5 minutes. Season the sauce with salt and pepper and red chili flakes, to taste. Remove toothpicks from the chicken. Drizzle the reduced cooking liquid over the chicken and serve immediately.