Preheat the slow cooker, if necessary; see the manufacturer's instructions. Heat the oil in a skillet, add the onion and eggplant, and fry, stirring, for 5 minutes or until softened and just beginning to turn golden.
Stir in the zucchini, capsicum, and garlic and fry for 3-4 minutes. Mix in the flour, then the tomatoes, stock, rosemary, and a little salt and black pepper. Bring to a boil, then spoon into the slow cooker pot. Cover and cook on high for 3-4, hours until the vegetables are tender.
When almost ready to serve, make the dumplings. Put the flour, ricotta, lemon rind, and a little salt and black pepper into a bowl. Add the egg and mix to a soft but not sticky dough. Cut into 12 pieces and roll each piece into a ball with floured hands.
Stir the ratatouille and arrange the dumplings on the top. Replace the lid and cook for 15-20 minutes or until light and firm to the touch. Spoon into bowls and eat with a spoon and fork.
