INDEX / FOLLOW LINKS==<meta name="robots" content="noindex, nofollow">||DO NOT INDEX / DO FOLLOW LINKS==<meta name="robots" content="noindex">||DO INDEX / DO NOT FOLLOW LINKS==<meta name="robots" content="nofollow">||DO NOT INDEX / DO NOT FOLLOW LINKS==<meta name="robots" content="noindex, nofollow">||DO NOT CACHE==<meta name="robots" content="noarchive">

Create a new TV (under elements tab) called "Robots" and past the following into the input field. Then apply it to all the templates of the pages you wish to see this TV option.
Set default to: <meta>
Set delimiter to: ||
Add the TV to the template header as [[*robots]] (v2+) or [*robots*] (v1 or less).

There's probably a more eloquent way of scripting with a snippet using instead the default MODx template variables of "Cacheable" and "Searchable"!

MODx TV for setting page visibility for robots

HTML