Nobody, no matter how preterist, will ever say that the scenes of the Second Coming and the New Jerusalem are set in Roman times, and are already fulfilled prophecy.
So let’s not exaggerate here!
Many parts of the Book of Revelation apply primarily to things happening during Roman times, while John was writing the book; and many parts primarily warned about things that would happen shortly.
However, all those parts apply secondarily to all times and places where Christians live, because we are always subject to persecution.
Likewise, there are some parts which are primarily talking about the Second Coming and the events surrounding that, although they have secondary application to all Christians in all times (including the original readers). As many Christian writers have pointed out, pretty much all of us will face death at some point, and that is the end of the world for us personally. (For most practical purposes, anyway.)
So you have to read carefully, and pay attention to the good teachers and teachings that the Church has handed down to us.
Scott Hahn’s book The Lamb’s Supper is a good starting point. If you are interested, there are also a lot of other good books about this, albeit a lot of them you will find in academic libraries or in translations that are online.
Here’s a good example that is quite short: Victorinus of Poetovio’s brief commentary on Revelation, with St. Jerome’s comments below. You will soon notice that it leans heavily on OT Scripture (which is pretty much a must, because Revelation does too!), but also that some of his early Christian interpretations are quite different from those you tend to see today.
(There are broad similarities among other early Christian commentaries, but they tend to disagree quite a bit also on various points! So one of the things the Church teaches us is that different people get different, valid things out of these Bible passages!)
