Convert your ruby app to run on JRuby (often fairly painless) then deploy it by generating a JAR file (should be reasonably painless) and copying it to the servers you're running on (should be bordering on trivial).
If you've never done Java programming, a JAR is a "Java ARchive" file which is basically a single ZIP file containing all the stuff your app needs to run. So you can install java on a new machine and copy the JAR file onto it, and you're ready to go.
The usual way of deploying a Ruby app is to write (or copypasta) some Capistrano recipes to have the production machines check it out from a git repo then build it in exactly the same way you do on your Mac. This has downsides: