It means to be a really bad runescape (or any game)addict. That means that you cannot even pretend to be a runescape(or any game) addict. You would like to get hooked on runescape(or any game) but you cant because you HAVE a life.
Guy:Hey man, I am addicted to runescape.
Other guy: No you're not you are too Broschh...
I am too broschh to be addicted to runescape.