Why do you need a Linux VDI? Test locally with the Rails server, then deploy to Heroku.
A linux desktop is entirely unnecessary. But so is Heroku.
This "just deploy to Heroku" mentality is really starting to get on my nerves.
Heroku is a great product that solves real problems for a certain class of project (and user). It is not, in any way, shape or form, the solution to every problem. Stop telling people it is.
if you need to get a rails app hosted NOW, it's as simple as
heroku create appname
git push heroku master