Marat Nepomnyashy

Overview:
At the time of this writing, the latest version of WordPress, version 4.7, 
 has functionality to discourage search engines from indexing the whole site, 
 but not functionality to discourage search engines from indexing only certain 
 specific pages and posts of the site.
Robots Meta Whiz is a WordPress plugin that allows site administrators to 
 deploy custom meta robots tags to discourage search engines from indexing, 
 following links from, caching, indexing images from, and / or have 
 additional custom restrictions on only for certain specifically-designated 
 pages and posts.
It is an easy way to discourage search engines from indexing only specific 
 pages / posts.
This only applies to search engine robots, and will not effect the site’s 
 local search functionality.
Technical summary:
Plugin works by hooking-in special logic into the action ‘wp_head’ to inject 
 the tag <code><meta name='robots' content='...'></code> with restriction directives for 
 the specified pages and posts.
Official project URLs:
https://wordpress.org/plugins/robotswhiz 
 https://github.com/maratbn/RobotsWhiz

Robots Meta Whiz

Easy way to discourage search engines from indexing only specific pages / posts with custom meta tags.

bettoadami

A Multisite Network plugin that removes the automatic sitemap link (deprecated practice) and adds custom parameters/lines at the end of the default Robots.txt whenever called. It will enable small adjustments for each site on the network – like pointing again to specific sitemaps if needed – without sacrificing the default conventions coded to WordPress’ core. To make the adjustments, look for a text area at the end of General Settings Page.

Robots.txt Extender

Dynamic robots.txt for Multisite! Change parameters, or don't, for each site of your network without losing the defaults from WordPress Includes.

Robots Meta Whiz vs Robots.txt Extender