Changes to the system functions in roles are audited in:
AUDIT_TRAIL table, with record_type = 'SFR'
Access type I = Insertion D = Deletion
You can use the below script to display any historical system functions that have been modified:
select * from audit_trail where record_type = 'SFR' and record_id like '%ROLE=(ROLE NAME)%' order by DATE_STAMP desc