If you feel like creating your own Random Maps for Return of Rome, you can, and the best way to start doing this is to read the extensive and most useful RMS guide made by
Zetnus, which you can find here: Age of Empires II Definitive Random Map Scripting Guide and Terrain RMS constants.
From experience: open any Random Map, and start carefully experimenting with whats possible. It's lots of fun creating them or building upon ideas.
I felt like posting this to garner some attention to the fact Random Map Scripting is now possible in Age of Empires 1 (Return of Rome), which is absolutely amazing. Expect to see some Random Maps for Return of Rome from me in the near future!