How To Create A File Archive in WordPress?

These are actually two questions. The second question – how to add categories to attachments – is already answered.

How to restrict uploading attachment to a specific role?

The capability to do that is named upload_files in WordPress. Some roles have this capability by default: authors, editors, administrators.

I would restrict it to editors and administrators. You can use a run-once plugin for that:

<?php
/* Plugin Name: Change Roles */

add_action( 'admin_notices', 't5_change_roles', 0 );

// Fires on the plugin activation screen just once.
function t5_change_roles()
{
    global $wp_roles;

    if ( ! isset( $wp_roles ) )
        $wp_roles = new WP_Roles;

    $existing_roles = get_editable_roles();

    foreach ( $existing_roles as $name => $role )
    {
        if ( 'administrator' === $name )
            continue;

        if ( 'editor' === $name )
            continue;

        $wp_roles->remove_cap( $name, 'upload_files' );
    }

    // Suppress "Plugin activated" notice.
    unset( $_GET['activate'] );

    print '<div class="updated"><p>Roles are updated, plugin deactivated.</p></div>';
}

But you can also use a plugin like Members and edit the roles per user interface:

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