Sprinkle both sides of fillets with salt and pepper. Sprinkle one side of each fillet with 1 rounded tablespoon of feta cheese and 1/2 teaspoon mint or other herb, if desired. Drizzle 1 teaspoon olive oil over each fillet.
Roll up each fillet from smaller end and secure with toothpicks. Grill over medium heat for 20-25 minutes or until fish flakes easily with fork. Place on a serving platter and garnish with parsley and tomatoes, if desired.
Note: You can also bake these fillets in the oven at 350° for 30 to 35 minutes. Thyme or oregano are good substitutes for the mint.