Civicrm Activities - Scheduling conflicts
" Is there anything in Civicrm that would notify the activity creator that there is already an activity scheduled for that date / time for that staff member?"

No there is nothing in CiviCRM that can do this currently.

For anyone using Drupal (I realise this user is on Joomla) then you could make a Views Calendar of Events and that could be used to view existing meetings, including filtering by contact.