So is it like an alternate universe to the other anime series? Starts out in the same point but goes differently? I've never followed the manga.

Well in the anime there was that last scene where Riza is looking after Roy at the end, which codes it fairly strongly for me. But no lovey dovey stuff or UST, it's true -- which I tend to like in het relationships. (I often judge my het pairings by transforming the girl in my head into a guy and seeing whether their relationship would still work for me, anyway.) I'm not a huge fan of Roy/Riza but I've always thought of them as the canon-intended couple.