If you really want to make a 3D game but don't know where to start, I suggest
Blender, which is a neat 3D modelling program with integrated game and physics engine.
I would assert that RO was probably made with a 3D modelling tool, a raster image editor, an IDE or text editor, and a C++ compiler and linker.
...
C++ is for pussies who can't deal with objects without help. C and assembly forever!