Complex sentence: The Blackburn Roc was a very similar aircraft developed as a "turret fighter" (its armament was in a dorsal turret) and the Roc was expected to serve alongside the Skua.
Split into simpler sentences: The Blackburn Roc was a very similar aircraft developed as a "turret fighter" with all its armament in a dorsal turret. The Roc was expected to serve alongside the Skua.