Before reaching the Umbral Field, Roan had spent months behind the fabric of space, wandering and trying to find a way out. It goes without saying that he travelled huge distances there, so it was simply impossible to tell where he had first appeared.
That said, after opening a Spatial Gate, no one would be able to tell exactly where the twins would come out. They might literally appear halfway to the other side of the Underworld. The only guarantee was that they would still be in the Underworld, as even the Fabric of Space has the division between the usual four realms of a Universe, like Heaven, Mortal World, Divine Realm, and so on.
*Crack, crack, crack...*
A Spatial Gate appeared deep underground, consuming all the dirt, rocks, and other debris in its surroundings. But as all that debris disappeared, Rean, Roan, and Kentucky shot out, Kentucky quickly turning around and closing the Spatial Gate perfectly.
