Script: Create an Azure Service Principal

<#
  .SYNOPSIS
  Create Azure AD Service Principal and Assign a role.

  .DESCRIPTION
  Create an Azure AD Application, an Azure AD Service Principal and then assign a given role.

  .NOTES  
    File Name  : CreateAzureADPrincipalAndRole.ps1
    Author     : Nilay Parikh
    Version    : 0.1

  .PARAMETER RMADAppDisplayName
  Specifies the new display name for the application.

  .PARAMETER RMADAppHomepage
  Specifies the new URL of the application homepage.

  .PARAMETER RMADAppIdenfierUris
  Specifies the new URIs that identify the application.

  .PARAMETER RmADAppPassword
  Specifies the password to be associated with the application.

  .PARAMETER RmRoleDefinitionName
  Name of the RBAC role that needs to be assigned to the principal i.e. Reader,   Contributor, Virtual Network Administrator, etc.

#>

[CmdletBinding()]
Param(

    [Parameter()]
    [ValidateNotNullOrEmpty()]
    [String]$RMADAppDisplayName,

    [Parameter()]
    [ValidateNotNullOrEmpty()]
    [String]$RMADAppHomepage,

    [Parameter()]
    [ValidateNotNullOrEmpty()]
    [String]$RMADAppIdenfierUris,

    [Parameter()]
    [ValidateNotNullOrEmpty()]
    [String]$RmADAppPassword,

    [Parameter()]
    [ValidateNotNullOrEmpty()]
    [String]$RmRoleDefinitionName
)

# Login to Azure
Add-AzureRmAccount

# Create an App
$app = New-AzureRmADApplication -DisplayName $RMADAppDisplayName -HomePage $RMADAppHomepage -IdentifierUris $RMADAppIdenfierUris -Password $RmADAppPassword
$applicationID = $app.ApplicationId.Guid | clip

# App Service Principal
New-AzureRmADServicePrincipal -ApplicationId $app.ApplicationId

#Wait
Start-Sleep 10

# Assign Role DevTest Labs User
New-AzureRmRoleAssignment -RoleDefinitionName $RmRoleDefinitionName -ServicePrincipalName $app.ApplicationId