probably Sasuke learned Kage Bunshin no Jutsu from Naruto but I don't think that he could perform the Rasengan if he only copies it from Naruto, remember that Rasengan needs a huge amount of Chakra which Naruto gets from Kyuubi. Second, I don't think Sasuke has mastered his Sharingan enough to copy such a high level technique like the Rasengan.