ORA-00904: ROWID: invalid identifier

SQL> create materialized view emp_dept
  2  refresh fast on statement
  3  as
  4  select e.ename, e.deptno, e.job, e.rowid, d.dname
  5  from emp e , dept d
  6  where e.deptno=d.deptno;
select e.ename, e.deptno, e.job, e.rowid, d.dname
                                 *
ERROR at line 4:
ORA-00904: "ROWID": invalid identifier

SQL> create materialized view emp_agg
  2  as
  3  select count(*), job
  4  from emp
  5  group by job;

Materialized view created.

SQL> create materialized view emp_rowid
  2  as
  3  select e.rowid, ename
  4  from emp e;
select e.rowid, ename
       *
ERROR at line 3:
ORA-00998: must name this expression with a column alias