I'd like to know that too...He was most likely not aware of every ability the rinnegan gifted him. Obito probably told him of it, Madara did inform Obito of the technique.
Though, is Nagato skilled enough to ressurect people and NOT die? Or. . Why would it kill Obito to bring back one person?
His body was destroyed by Naruto and i believe that it would be no use ...its not like his power would remain the same its just a body used to plant chakra in