This plugin has been closed as of 2022年4月26日 and is not available for download. 原因：安全性問題。
I tried pro version for add robots.txt for my multisite but i does not work and the support does not respond.
Great multisite plugin for robots.txt
This plugin is two versions and two months out-of-date. A more recent stable version, 1.0.14, released and tested for WordPress version 4.8.3, is available on GitHub. Curiously, the documentation on GitHub for this plugin even recommends installing the plugin thru WordPress.org.
Cool, but I want to add Host directive for ever site of multisite system.