Rinse the grape leaves under cold water to remove any excess brine or salt, and then place them in a large bowl filled with warm water for about 10-15 minutes to soften. Drain and pat dry with paper towels.
In a medium-sized pot, bring 2 cups of water to a boil. Add the rice and 1/2 teaspoon of salt, then reduce the heat to low, cover the pot, and cook for 15-20 minutes or until the rice is tender and all the water has been absorbed.
In a large bowl, combine the cooked rice, chopped onion, parsley, mint, dill, olive oil, salt, black pepper, cinnamon, and allspice. Mix well until all the ingredients are well combined.
Place one grape leaf on a flat surface with the shiny side down and the stem facing you. Spoon about 1 tablespoon of the rice mixture onto the center of the leaf.
Fold the bottom of the leaf up over the filling, then fold in the sides and roll the leaf tightly into a cylinder. Repeat this process with the remaining grape leaves and filling.
Arrange the stuffed grape leaves in a single layer in a large pot, then pour in the vegetable broth and lemon juice. Cover the pot and bring the liquid to a boil over medium-high heat.
Reduce the heat to low and simmer for about 45-50 minutes, or until the grape leaves are tender and the filling is cooked through.
Remove the dolmas from the pot using a slotted spoon and arrange them on a serving platter. Serve hot or cold, with lemon wedges on the side.