Reason behind reviving oro

[Naruto insane killer]

As we all know that RDS was taught to Sarutobe by Minato and IMO they both share same death demon. It is possible that when uzumaki clan members found how to reverse RDS from the death demon when necessary they must have created various death demons for the purpose that they know whose sole is traped in which demon.The mask at the uzumakis shrine were used to resemble various deathdemon . Oro was important part of plan because he has seen the face of the deathdemon used by sarutobe and to use edo tensi and to be able to be alive after rescuing their sole oro was only the perfect man for job

 

[Uchiha Josephus]

Also, the fact that he could cheat death made him perfect for the job.

Hence why Sasuke said "There are certain things that only Orochimaru can do"

But the mask thing seems legit too.

 

[SpiritNinja]

Because ORO is the greatest boss of all TIME

 

[zamki]

Dat damn snake*sarcasm*

 

[Naruto insane killer]

Also it wont require any delay in learning and perfecting edo tensi when they had the man who was like all in one for doing the job.