Numerous dependencies don't get installed with "drush en -y" command for rooms module
Drush will only check the .info file for dependencies, in the case of the Rooms module those are:

dependencies[] = date
dependencies[] = date_api
dependencies[] = date_popup
dependencies[] = jquery_update
dependencies[] = libraries (&gt;=2.x)
dependencies[] = variable


If Drush is missing any of those out, you have a buggy version of Drush and need to get an issue opened for it (or check for a similar existing one).

Other than that any "missing" dependencies are either down to a bug in the Rooms module, or your expectations being incorrect.

For example, maybe you're expecting Drush to auto-download all of the dependencies for the sub-modules included with Rooms as well? 

It won't, those are considered separate modules. If you want those dependencies downloaded/installed automatically, you'll need to run drush en for each module individually.