You can try the following code.
Can get the response without a POJO class by getting using ResponseBody format and then you can parse it normally like ordinary JSON parsing.
Api Call:
Call<ResponseBody> call = service.callLogin(AppConstants.mApiKey, model_obj);
    call.enqueue(new Callback<ResponseBody>() {
        @Override
        public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
            if(response.code() == 201)
    {
     JSONObject jobjresponse = null;
    try {
            jobjresponse = new JSONObject(mResponse.body().string());
            String status = jobjresponse.getString("status");
            JSONObject  result = jobjresponse.getJSONObject("results");
                    String  msg = result.getString(“msg”);  
} catch (JSONException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }       
        }
        @Override
        public void onFailure(Call<ResponseBody> call, Throwable t) {
        }
    });
Retrofit Interface class:
public interface RetrofitInterface {
@Headers({"Content-Type: application/json", "Cache-Control: max-age=640000"})
@POST("v1/auth/")
public Call<ResponseBody> callLogin(@Query("key") String key, @Body LoginModel body);
public static final Retrofit retrofit = new Retrofit.Builder()
        .baseUrl(“base url”)
        .addConverterFactory(GsonConverterFactory.create())
        .build();
}
Sample Response:
{ "status":"true", "result":{"msg”:”created successfully”} }