How do I restrict access for certain content to certain roles?

I am trying to restrict certain content, pages, posts and possibly CustomPress types to certain member levels. I assume it's much harder to restrict by category, but if not, cool! I want to do this the easiest way working alongside any plugin that may be appropriate: I need to document certain things that can only be seen and navigated by site admins. This is for upper level management. I need to give them an easy way to view and search specific documentation that must be completely hidden from other support staff, even on searches. I tried Membership to create a post category to start with for these, then figure out how to display and organize, but did not see this option to build this from very easily and apologize if I just overlooked it. I am OK creating a completely different content type with CustomPress if it will allow me to add this security restriction. What I create must be easy to navigate and search and filter for upper level management for them to get the most out of this documentation. Any guidance would be much appreciated.
Thank you!