There are a number of libraries to use for graphics, Stitchs mentioned some of them. I personally only have experience with SDL and to some extent Allegro, SDL a very good choice if you want your games to run on different platforms, you can successfully compile your code on any platform basically without having to change your code (the only thing that you have to change is the line(s) where you include SDL). You can also use OpenGL on top of both SDL and Allegro for more advanced rendering such as body rotation and 3D rendering.
http://lazyfoo.net/ is a very helpful website if you want to learn SDL.
I don't really know much about SMFL and DirectX and that, but you could probably just google them if you want some more information, I know SMFL has quite a lot of tutorials/guides.
One thing I want to say when it comes to making an RPG is that you have to think about what you're going to implement into the game and how you're going to implement it, I know from experience that things tend to go out of hand very quickly if you don't (as in very bad code design which leads to very annoying bugs and so on).