Hi Brian,
Since I don't use Active directory, I can't give you a very good answer.
"Security for Microsoft Visual Basic .Net", isbn: 0-7356-1919-0 talks about
getting the user's name and domain from WindowsIdentity.GetCurrent.Name and
using that name to search Active Directory for the roles that user belongs
to. I'm not sure what namespace that comes from, but the code example imports
System.DirectoryServices, System.Threading.Thread and
System.Security.Principal.
hth
Tom