[SmG Nukem]

I have seen this situation a few times in the past, both as a Mod and as an Admin on a few different servers and groups.

Any changes made should be approved by those in charge as a group and not done ad hoc by one or two individuals.
There must be an agreement by all or at the very least consultation otherwise things can get very ugly very quickly.

As Mods you probably should not have made the change yourself but discussed it first.
Have a group discussion with the owner and the other Mods to iron out the reasons why it happened and how to move on in the future.
The owner may have very good reasons for not creating the role that you don't know of.