Single User Windows version of Roll Call
You can find the name and location of your data file on the main Roll Call splash screen.  It is found on the lower left corner of the window.  Typically the data file on a windows machine is found:

C:\BytheBook\RollCall9.5\Database\Rollcall.4dd (your file name may be different)

Single User Mac version of Roll Call
You can find the name and location of your data file on the main Roll Call splash screen.  It is found on the lower left corner of the window.  Typically the file on an OSX machine is found:

HD:Applications:RollCall:RollCall.4dd

Multi-user System
If you are using the multi-user version of Roll Call, you can still determine the name and location of your data file through the Roll Call Client screen.  It is found on the lower left corner of the splash screen window.