Hi, I look after the roster at Lockyer Valley Regional Council.  I currently look after them through an excel spreadsheet, which is colour coded.
We currently have 8 full time staff, which includes myself and the Project Officer, 3 Part time staff and 4 casual staff and 2 vacant positions.
Depending on the month is how I determined how many I can leave on leave.  Usually I can only allow 2 staff at a time.
We have a Gatton Office and a Laidley Office so both these offices have front counters where two Customer Service Officers are rostered on daily.  The Laidley Office currently has a QGAP facility as well.
Laidley counter have two staff, these staff look after Live Chat. Remittance payments by credit card,E-Request and QGAP and council receipting and other Council business.
The Gatton counter two staff are allocated Remittances of cheque payments through the mail.  also help out on Live-Chat when they are not in a busy period. Collect payments and look after other Council business. 
During more busier periods these counters will have three staff, which then I would use a casual to fill this position.
In the call centre we tried to have 4-5 Customer service Officers depending on the call demand and business of the month.   These officers look after our monthly hall & showgrounds enquiries and bookings and cemetery enquiries and bookings, preparing of mail for post office.  The call centre staff also log onto Live-chat .
When preparing rosters I look after the reception desk first then allocate the call centre staff then I will back fill with casuals, which seems to be everyday as I currently have two positions vacant that I am waiting to fill.
The staff are rostered around and I tried not to allow them to do the same task anymore than 2 days in a row.
Staff also move branch to branch but at the moment is limited by QGAP trained staff.
Happy to send you an excel spread sheet if that helps
Thanks Wendy