Hi,
First check to see who as privileges to perform these type of actions
Check the dba_role_privs to see if anyone else has the DBA privilege
select grantee from dba_role_privs
where granted_role = 'DBA'
Next alter system privilege DROP ROLLBACK SEGMENT
also check ALTER ROLLBACK SEGMENT the same way
select grantee from dba_sys_privs
where privilege like 'DROP ROLLBACK%'
If you find someone has the privileges who shouldn't (apart from the IMP_FULL_DATABASE role. Communicate your concerns the offending parties.... be nice ;>
Next if this is not the problem,
Check the alert log for any trace files or errors which might have caused this to happen
I never heard of rbs going offline unless on restart they are no specified correctly in the init.ora file.
Being dropped automatically sounds fishy.
This might sound like Oracle Support, but it would be better to get moving on an upgrade, as from the end of September 8.1.7 will the designated stable and free bug fix version.
Performance... Push the envelope!