Create dB and initial rollback segs

When the create dB statement is issued, is there automtically a SYSTEM rbs in the datafile '/u01/app/oradata/DW1/system.dbf' (see below create dB)?

Is the next step to create a 2nd rbs in the SYSTEM t/s? Why the system tablespace?
Why don't I just create subsequent T/S's for the new additional rbs's at this time rather
than putting the new rbs in the system tablespace?

Would the next step be to create more tablespaces for more rbs's? (We want to use 10 rbs all together)

Thanks
Frank S.

CREATE database "DW1" maxinstances 1 maxlogfiles 16 character set "US7ASCII"
datafile
  '/u01/app/oradata/DW1/system.dbf' size 262144000 reuse logfile

  group 1 ('/u01/app/oradata/DW1/redo01a.log',


           '/u02/app/oradata/DW1/redo01b.log') size 262144000,


  group 2 ('/u01/app/oradata/DW1/redo02a.log',


           '/u02/app/oradata/DW1/redo02b.log') size 262144000,


  group 3 ('/u01/app/oradata/DW1/redo03a.log',
            /u02/app/oradata/DW1/redo03b.log)  size 262144000,
  group 4 ('/u01/app/oradata/DW1/redo04a.log',


           '/u02/app/oradata/DW1/redo04b.log') size 262144000;