What was the role and importance of history in the classic book 1984?
Put simply, history does not exist in 1984. Of course, in one sense it doesn't "exist" anywhere because the past exists in memory (although there are lots of books, visuals, etc., but most of these represent someone's memory of the past and not the actual event; this is a complicated discussion and probably not what you need.
In 1984 those who control the present control the past; they are literally able to "invent" the past because there is no objective record of anything that happened. History is just a tool for propaganda. If they want to look better that their predictions, or if they failed to live up to their prediction, they simply edit the "records" of the past to "sync" the present. This gives them the ability to control the future.
Although this may seem wierd, it happens whenever we fail to check to see if what our government is telling us is "true." I suspect we are a lot more like 1984 than we would like to believe ...