Solution:
Actually the third parameter of the add_options_page() function is a capability which is different than a role.
Another way to think of it is to say, “A role can do these X number of things called capabilities. Some capabilities are ‘doable’ by several roles.”
Taking a look at the function signature from the documentation we can see they’ve defined the parameter name to be capability.
<?php
add_options_page( $page_title, $menu_title, $capability, $menu_slug, $function);
?>
I would take a look at this chart of Roles & Capabilities and choose a capability that only an Administrator would have (preferably one closely related to the feature you’re building in your plugin).
For example, I might choose manage_options (just as you’ve done) as it reflects fairly closely what you’re trying to build ct_admin_settings_page to do.