1. In a mixing bowl, combine rice, parsley, mint, tomatoes, onion, olive oil, salt, and black pepper.
2. Place a grape leaf on a flat surface, shiny side down. Add a spoonful of the rice mixture in the center.
3. Fold the sides of the leaf over the filling and roll tightly.
4. Repeat with remaining grape leaves and filling.
5. Place the rolled grape leaves in a pot, seam side down, in a circular pattern.
6. Add water to the pot, enough to cover the grape leaves.
7. Place a plate on top to keep them from unrolling during cooking.
8. Bring to a boil, then reduce heat and simmer for 1 hour.
9. Let cool before serving.