Heat oven to 400° F. Line baking sheet with aluminum foil; spray with nonstick cooking spray; set aside. Place one chicken breast between sheets of waxed paper. Pound until chicken breast is ¼-inch thick. Repeat with remaining chicken.
Place chicken breasts flat on work surface. Lay spinach leaves on top of each chicken breast. Cut Mozzarella cheese into 4 equal pieces (1/2-inch wide x 2 ½-inch long). Place in center of chicken. Gently roll up.
Brush outside of chicken with olive oil. Stir together breadcrumbs, grated Parmesan cheese and salt. Gently roll outside of chicken in crumb mixture coating outside completely. Place tightly rolled chicken, seam side down, on prepared baking sheet.
Bake 22-26 minutes or until chicken is no longer pink. (Cheese will melt outside chicken slightly.)