Preheat oven to 425 degrees.
Place steaks between 2 sheets of plastic wrap and pound to 1/16-inch thickness using a meat mallet or small heavy skillet. Sprinkle steaks with salt and pepper.
Place cream cheese, sun-dried tomatoes, and Parmigiano-Reggiano in a blender of food processor; process until blended. Spread 1/2 of cheese mixture on each steak.
Top with spinach. Roll up steaks; secure with wooden picks. Cut each roll in half crosswise.
Heat a large cast-iron skillet over medium high heat. Coat pan with cooking spray. Add rolls to pan; cook 6 to 7 minutes or until browned, turning frequently.
Place pan in the oven. Bake at 425 degrees for 10 minutes or until desired degree of doneness.