The module azure_rm_virtualmachine has fields for plan information. Module azure_rm_virtualmachinescaleset needs to have them and forward them when creating a VM with an image that requires plan info to be specified. The CIS hardened images from the Azure Marketplace is a prime example.

upgrade_policy: Manual
    subnet_name: testsubnet
    admin_username: adminUser
    admin_password: password01
    managed_disk_type: Standard_LRS
    image: customimage001
- name: Create a VMSS with a custom image from a particular resource group
  azure_rm_virtualmachinescaleset:
    resource_group: myResourceGroup
    name: testvmss
    vm_size: Standard_DS1_v2
    capacity: 2
    virtual_network_name: testvnet
    upgrade_policy: Manual
    subnet_name: testsubnet
    admin_username: adminUser
    admin_password: password01
    managed_disk_type: Standard_LRS
    image:
      name: customimage001
      resource_group: myResourceGroup
'''
RETURN = '''
azure_vmss:
    description:
        - Facts about the current state of the object.
        - Note that facts are not part of the registered output but available directly.
    returned: always
    type: dict
    sample: {