bbp_profile_update_role( int $user_id )

function bbp_profile_update_role( $user_id = 0 ) {

	// Bail if no user ID was passed
	if ( empty( $user_id ) )
		return;

	// Bail if no role
	if ( ! isset( $_POST['bbp-forums-role'] ) )
		return;

	// Fromus role we want the user to have
	$new_role    = sanitize_text_field( $_POST['bbp-forums-role'] );
	$forums_role = bbp_get_user_role( $user_id );

	// Bail if no role change
	if ( $new_role === $forums_role )
		return;

	// Bail if trying to set their own role
	if ( bbp_is_user_home_edit() )
		return;
	
	// Bail if current user cannot promote the passing user
	if ( ! current_user_can( 'promote_user', $user_id ) )
		return;

	// Set the new forums role
	bbp_set_user_role( $user_id, $new_role );
}