Well the fact is that we don't know, whether or not, he had rinnengan before or after sealing the Juubi. But what we do know, is that he had rinnengan when he started to travel the world and spread/teach ninjutsu as a way to create peace.
Conclusion:
If we are told, whether he was jinchuriki before or after he traveled the world to spread ninjutsu, we will have the answer.
And just saying that rinnengan must come from Juubi since it looks alike is somewhat idiotic, but you may say that it "seems" like it has something to do with the Juubi.
However, one thing bothers me about this. In order to become jinchuriki of the juubi, you need the rinnengan, cause it is the only way to summon / use the shell of the juubi to store all the bijus.
So this questions this so called "look alike"-theory a lot, and it really suggests that rinnengan shouldn't be connected to the Juubi.
Besides it was the ridukou senin who gave the 9 beasts their different powers. Not the Juubi. Though it might be the Juubi that gave the ridukou senin the ability to give them such powers xd