// Only need to load a page once to get this into db, then comment out (or place in theme/plugin activation)
// WP Codex: http://codex.wordpress.org/Roles_and_Capabilities
$result = add_role(
	'basic_contributor',
	__( 'Basic Contributor' ),
	array(
		'read'         => true,  // true allows this capability
		'edit_posts'   => true,
		'delete_posts' => false, // Use false to explicitly deny
	)
);
if ( null !== $result ) {
	echo 'Yay! New role created!';
} else {
	echo 'Oh... the basic_contributor role already exists.';
}

// Or remove a role
remove_role( 'basic_contributor' );