Combine the black beans, salsa, and rice in a saucepan and simmer gently for 3 minutes, stirring occasionally. Remove from heat, cover, and let sit for 5 minutes. In an un-greased skillet, heat a tortilla for a minute or two until warm and soft, then spread a line of the bean mixture down the center. Top with lettuce, tomato, green onion, and more salsa, if desired. Wrap the tortilla around the filling, then repeat with the remaining tortillas.