Here is even a WMI method to do it, you'll need to convert it for use for multiple computers.

ADSI of an OU or NETVIEW 1.2 would be much faster though.


Code:
$strComputer = "."
$objWMIService = GetObject("winmgmts:" + "{impersonationLevel=impersonate}!\\" + $strComputer + "\root\cimv2")
$colComputers = $objWMIService.ExecQuery("Select DomainRole from Win32_ComputerSystem")
For Each $objComputer in $colComputers
    Select
        Case $objComputer.DomainRole=0
            $strComputerRole = "Standalone Workstation"
        Case $objComputer.DomainRole=1
            $strComputerRole = "Member Workstation"
        Case $objComputer.DomainRole=2
            $strComputerRole = "Standalone Server"
        Case $objComputer.DomainRole=3
            $strComputerRole = "Member Server"
        Case $objComputer.DomainRole=4
            $strComputerRole = "Backup Domain Controller"
        Case $objComputer.DomainRole=5
            $strComputerRole = "Primary Domain Controller"
    EndSelect
    $strComputerRole ?
Next