Combine the ricotta, cream cheese, and sugar in a food processor; process until smooth.
Split the ladyfingers in half lengthwise. Arrange 24 halves in a single layer in an 11 x 7-inch baking dish. Drizzle with half the Kahlua, and let stand 5 minutes. Spread half of cheese mixture evenly over the ladyfingers. Repeat procedure with the remaining ladyfingers, Kahlúa, and cheese mixture. Sprinkle with cocoa.