in rollplay (roleplay?) you mean pen&paper game such as d&d or exalted, right? if so, are you making a game system (such as d&d), a setting (such as forgottem realms) or both (such as exalted or world of darkness)? in any case, i would recommend to read the dark sun setting. it is quite interesting and have some common ideas with your creation. i would also recommend checking some dedicated forums for roleplaying, like giants in the playground and enworld. many people there are extremly nice and could help you make your creation. best of luck!