Well im not writing it for you 
... but check these objects out:
mydb..sysmembers: contains a row for each member of a database role
master..syslogins: hooks to mydb..sysusers over the sid column
master..sysdatabases: loop for all these
Cheers
Ck
Chris Kempster
Author of "SQL Server 2k for the Oracle DBA"
Chris Kempster
www.chriskempster.com
Author of "SQL Server Backup, Recovery & Troubleshooting"
Author of "SQL Server 2k for the Oracle DBA"