You don't need a Ragnarok Online developer specifically to help you set up and run your own private server. You need a person who has experience running private servers and you can easily find someone online around the mmorpg communities like WoW for example. You would be better off trying to find someone on a more specialised forum than this though.
If you are planning on running the server for free and collecting donations for premium items there are surely people out there who could help you for a fee.
I am currently looking also on herc and athena forum. Just wanted to post it here, since I am fairly familiar with this forum. I think a dev might be needed as things are looking messy as the original owner said that there were problems relaunching the server as it has a lot of incompatibilities with the new emulators.