Oracle "Import from Export Files" screen refusing both SYSADMIN and Normal users
The SYSMAN account is for adminstering Enterprise Manager, rather then the database; see the predefined user accounts. I would shy away from modifying anything about any of those accounts, even granting an additional role, unless specifically told to by Oracle.

The first message you got says that import isn't supported when logged in with the SYSDBA role. That doesn't mean you can't import as SYS, just that you have to log in as SYS with the NORMAL role rather than as SYSDBA.

This assumes you want to do a full import though; for partial (e.g. schema-level) imports you might want to create the user first and perform the import as that user, but I'm not sure that's what you're looking for at the moment.