Lando is the epitome of a supporting character. In ESB he has very little screen time. Hell, he's not even in it until it's over half over. In RotJ, he gets just slightly more screen time than Admiral Ackbar due to his cameo appearance in Jaba's palace and his presence at the Sarlacc pit. Other than that he's no where near the big 3 through the rest of the film... just plays an important supporting role to show the progress of the space battle.