deployer/recipe/deploy/rollback.php

<?php
namespace Deployer;

use Deployer\Exception\Exception;

desc('Rollback to previous release');
task('rollback', function () {
    $releases = get('releases_list');

    if (isset($releases[1])) {
        $releaseDir = "{{deploy_path}}/releases/{$releases[1]}";

        // Symlink to old release.
        run("cd {{deploy_path}} && {{bin/symlink}} $releaseDir {{current_path}}");

        // Remove release
        run("rm -rf {{deploy_path}}/releases/{$releases[0]}");


        writeln("<info>rollback</info> to {$releases[1]} release was <success>successful</success>");
    } else {
        throw new Exception("No more releases you can revert to.");
    }
});