Action [indices:admin/delete] is unauthorized for user

Elastic Stack Elasticsearch
4

Update:

I have corrected this roles.yml now,

>  x-pack]$cat roles.yml
> # The default roles file is empty as the preferred method of defining roles is
> # through the API/UI. File based roles are useful in error scenarios when the
> # API based roles may not be available.
>   testing:
>   run_as: 'hello'
>   cluster:
>     - all
>   indices:
>     - names: 'twitter'
>       privileges:
>        -delete_index

Somehow, I get the same error,

 >   x-pack]$curl --user hello:hello123 -XDELETE  '10.245.30.45:9200/twitter?pretty'
> {
>   "error" : {
>     "root_cause" : [
>       {
>         "type" : "security_exception",
>         "reason" : "action [indices:admin/delete] is unauthorized for user [hello]"
>       }
>     ],
>     "type" : "security_exception",
>     "reason" : "action [indices:admin/delete] is unauthorized for user [hello]"
>   },
>   "status" : 403
> }