This largely depends on how the organization defines that job. . .
It could range from "everything" to some subset of responsibilities.
Often a CICS Admin supports all of the active CICS regions on the system or lpar which includes (but is not limited to) product install/upgrade, applying fixes, problem resolution, performance issues, configuration of the CICS regions, etc.
Some of the organizations i've supported have an entire team of CICS Admins while others have a single CICS Admin who also has other responsibilities. . .
Hope this helps,