Hey @Kavya, try something like this:
- name: Create a VM with managed disk
  azure_rm_virtualmachine:
    resource_group: Testing
    name: vm-managed-disk
    admin_username: adminUser
    availability_set: avs-managed-disk
    managed_disk_type: Standard_LRS
    image:
      offer: CoreOS
      publisher: CoreOS
      sku: Stable
      version: latest
    vm_size: Standard_D4