Rohan online to be is not the best game in the world. I gave the game a try a long time ago while it was in Japanese. I did not play the game to much so the review wont be to big.
I'll start off with the classes

Human KnightThese are the human race type class. While most people dont like them becuase of the weaker stat types, in this game you dont have to worrk about that. 

Human Knight DefenderA brute of a solider, they are often the center of a battle party due to their strengthened defense. This makes them perfect tanks. The other thing that backs this up is their ability to cast many stun spells.

GuardianThese steadfast warriors boast refined attacks skills. They can successfully reach their targets even if well-protected, but what makes these true warriors is their combo skills. With each hit the damage can increase.

Elf Healer These elf healers spend their time in the back of the party making sure that you dont die. They come with many healing and buff spells. When pu to the test they can also use powerfull magical attacks to fend for themselves 

PriestSpecializing in healing and protection using a range of powerful magic spells. They assist by buffing the party members so they can better fight.

TemplarQuite the aggressor, they are more of the fighting type healers who only use their magic on themselves. If needed they can be used in a party but wont be as much help as the Priest.
 

Half ElfOffsprings from the Human and Elf, these forest-dwellers are masters of ranged combat. Be it bow or arrow or mechanical crossbow, their proficiency is unmatched. They are able to shoot from the farthest distance by useing spells that help increase the distance. 

RangerWell versed on the crossbow, Rangers dominate their opponents with swift and precise arrow and dagger attacks. By using corssbows they attack slower but with thier powerfull attacking skills it dose not matter much.