Simple configuration, all vm's with role == server should get user01 and all vm's with role == webserver should get apache installed.

LinuxConfiguation.ps1

Configuration LinuxConf
{
    Import-DscResource -ModuleName nx

    Node $AllNodes.Where{$_.Role -like "*server"}.NodeName
    {
        nxUser NewAccount
        {
            UserName = 'user01'
            Ensure = 'Present'
            FullName = 'A User'
            Password = 'P@ssw0rd!'
            HomeDirectory = '/home/user01'
        }
    }
    Node $AllNodes.Where{$_.Role -eq "webserver"}.NodeName
    {
        nxPackage Apache
        {
            Name = 'apache2'
            Ensure = 'Present'
            PackageManager = 'Apt'
        }
    }
}

$MyNodes = 
@{
    AllNodes = 
    @(
        @{
            NodeName = 'ubuntu'
            Role = 'server'
        },
        @{
            NodeName = 'web-01'
            Role = 'webserver'
        }
    )
}