Not sure why it's saying there is no case for admin? The second case checks for this.

<?php
//Available roles: admin, editor, author, subscriber
if (!isset($role)) {
    $role = 'subscriber';
}

//change to switch statement
switch ($role) 
{
    case ('editor') :
        echo "You do not have access to this page. Please contact your administrator.";
        break;
    case ('admin') :
        echo "As an admin, you can add, edit, or delete any post.";
        break;
    case ('author') :
        echo "You do not have access to this page. Please contact your administrator.";
        break;
    case ('subscriber') :
        echo "You do not have access to this page. Please contact your administrator.";
        break;
    default:
        echo "You do not have access to this page. Please contact your administrator.";
        break;
}