This is a great question, and I personally think that Sasuke's Rinnegan is problematic and a topic blown up by his fans. We have argued about this many times, but most fanboys will not accept it as a fact - That is what Sasuke has is not a Rinnegan. There are many reasons to prove it.
(1) Rinnegan is the power of the chakra of Hagoromo - the Rikudo Sennin
(2) Rinnegan can be unlock by Indra's reincarnation only after he has taken the chakra of Ashura's reincarnation
(3) When talking to Naruto, Hagoromo clearly stated that Madara obtaining Rinnegan was a problem. Basically, Hagoromo did not like it.
What are the interpretations of the above?
(a) From point (1), if Sasuke's eye is really a Rinnegan, then it means Sasuke has all Hagoromo's chakra power.
(b) From point (2), if Sasuke's eye is really a Rinnegan, then it means Sasuke also has Ashura's power just as Madara did have Hashirama's power when he took his cells.
(c) From point (3), if Sasuke's eye is really a Rinnegan, then it means Hagoromo is simply stupid to say something and do another thing.
Obviously, you can see that Sasuke does not have all Rikudo's chakra power, and he does not have Ashura's power either. Besides, I believe that Rikudo is not stupid. Thus, I still maintains that Sasuke's eye is an updgrade to his left Sharingan to its ultimate power - that is the final Tsukyomi. Tsukyomi can manipulate time, and create powerful illusion. Thus, Sasuke's role in the fight will be to cancel the Tsukyomi with his super Sharingan.