Rotaville allows you to schedule any employee to any shift.
The shift assignment menu has now been updated so that employees who are already assigned to another shift at same time or who have a holiday now have their names struck out
like this. This will help managers from double assigning an employee. It's still possible to assign them though if you wish.
Here is an example screenshot showing currently assigned employees with their names struck out.
The same feature is also available on the mobile site