Question: Is it possible to limit access to a page using wordpress user roles that isn't included in the wordpress install.

For example I have a CS Cart install with only a couple of products but I need to limit access to these pages to certain users.

Can I add something in to my CS Cart install to call on Wordpress to be able to limit access if the user is just a subscriber?

Answer: 
if you can include the `wp-load.php` from WP install; after this you can use all WP Core functions and can also check the user and his rights with core function - `current_user_can()`.

But maybe it's easier to create an bridge from CS Cart to WP, if CS Cart has an own user table; i dont know.
If you just need to restrict to a specific WP page (that the CS cart is embedded within it with a [shortcode] or something, I presume - I don't know CS cart), the best way of doing this is by using one of the role managers plugin.

This one - [User Access Manager](http://wordpress.org/extend/plugins/user-access-manager/) - is a bit out of date, but it handles specific page restrictions out of the box. check it out & see if it fits.