Roles and permissions

Sorry but this post is going to be a bit lazy on my part as I've played about with roles and can't get what I want. I'm hoping somebody might just know.

I want to create a 'subadmin' role. A user that can create courses and categories as well as create/delete users and edit their profiles. I do not want these users to be able to modify the front page but I do want them to have a small admin menu showing the admin sections they have access to.

Can anybody help? I've tried but can never seem to get it exactly right.