Then I can deploy with a single command?
I have done this a ton of times with Capistrano but it's always a pain in the ass for new projects because I need to install Nginx, PostgreSQL, RVM, Ruby version, etc etc etc. Lots of busywork I don't really care about.
It uses Heroku buildpacks to build self-contained containers with all your dependencies with one command: building containername
DO has a Dokku vm you can select when you spin up a new droplet.