Let me guess, first semester IT student, just started a 1-4 weeks ago and now wanting to go full aggro on developing?
If you want to do serious development, here is not the proper place to ask. To do proper game modding you need to focus on skills apart of that certain game (in this case rohan)
You dont need to know how to setup a rohan server. Neither do you have to know any specifics about the game. The first step for you should be to learn c/c++ in its full extends and PROPER so you can count it down while asleep. After that, get reverse engineering skills, how does data look on-disk. After that, get into modern virtual languages like Java/C#. Get into game development, what methods do exist. Hows stuff done. Same for networking and databases. And maybe than, you might be able to start a little with game modding.
Now to clarify. Every idiot can setup a server. Every idiot can run a server. Every idiot can edit bins. Is that modding? No it isnt, at least not real modding, its just messing with the server configuration, but nothing indepth at all. However, real modding and real development does require way more, to be able to acctually change the game and implement various stuff. Be it EM/IM, be it services, be it new game systems. To do that, you need a huge knowledge and background, you need to dive into various regions of IT day after day, every day for several hours. You need to practice alot and eventually youll be able after YEARS of work to acctually accomplish everything you want.