It would be a good habit to include in each role a dump of wikipages for

• documentation; at a minimum a link to the mw.org docpage, plus any vagrant-specific documentation if needed.
• test pages/showcases, i.e. predefined files for a media handler extension, a sandbox with various examples for a parser extension... (Lightbox demo is an example of a test page for MediaViewer which we replicate by hand to vagrant boxes we use and it's not super user friendly.)

Such pages should be accessible from the main page, but different roles/dumps cannot share the same page, so there should be some system to do that. Here is a simple proposal: have these pages conform to the naming convention VagrantPage[role name][*], and replace the default MediaWiki startpage with {{Special:Prefixindex/VagrantPage}} (plus some links to vagrant documentation / info on the vagrant roles add command).