Long hair is more flattering for those with round faces although you should avoid having it all the same length. Add some layers around your face for definition.
What Haircut Looks Great For Girls With Round Faces?
Layered hair is perfect but keep it long since short hair makes it look like you have a fat face.
Having a round face is not that bad. There are hairstyles to keep and hairstyles to avoid. There are some hairstyles that can compliment a round shaped face, as well as make a round shaped face appear larger than it really is.
Shoulder length hair (layers are optional) a side swept bang cut about half way down to your nose always and I mean always looks good on someone with a round face, blow dry it using a round brush and it should look really nice