If you have a person in your database that does not have any associated donation records you can delete them by simply calling up their record and clicking on the DELETE RECORD button in the Edit Person window.

If the people you wish to delete have contributed, you'll need to use the Global Delete funtion.  Please note the global delete, deletes entire families.  It's also a good idea to perform a backup before proceeding.  To do the delete:

1)  Select Admin>Global Changes from the main Roll Call window
2)  Mark the selection for Global Delete People
3)  Click through the series of warning messages
4)  Perform a query that will return the people you want to delete
5)  Click OK to delete all the people in your list