Error: BULK_SEND_ROLE_NAMES_MUST_BE_UNIQUE

I am using Docusign.eSign .NET package to integrate with docusign. I am trying to use BulkEnvelopesApi.CreateBulkSendRequest. I have two roles - Admin and Supervisor and I am assigning two emails to each of these two roles something like this (captured the model as JSON)

{
   "bulkCopies":
  [
  {
    "recipients":[
      {"email":"admin@contoso.com","name":"Admin","roleName":"Admin"},
      {"email":"supervisor-1@contoso.com","name":"Supervisor-1","roleName":"Supervisor"},
      {"email":"supervisor-2@contoso.com","name":"Supervisor-2","roleName":"Supervisor"}]}
    ],
    "name":"Demo"}
  }
  ]
}

Now, when I call createbulksendlist, i get the error BULK_SEND_ROLE_NAMES_MUST_BE_UNIQUE. I believe this is because I have Supervisor role twice in the JSON. So how do i send the request where multiple recipients share the same role?