Roof Rails was made using only Unity 3D with C# language. Unity 3D is the easiest Game Engine which was ever made.
Making Games like Roof Rails
Thousands of people are afraid to getting started in developing games like Roof Rails, which is now a days very easy now a days, Look at the Unity which is the best gaming engine which was ever build specially for the Indie Game Developers, Roof Rails Game Engine is also Unity 3D. Unity is the best Gaming Engine for the people who wants to work individually. The best part is Unity 3D is using C# language which was build by Microsoft and known to be the second easiest language to learn as your first language.
There are Thousands of tutorials on Internet which help you on your journey to Game Development Industry, Also Unity Documentations is also very easy and well described.