Are there any instructions on searching rifts for items I rolled a "falling Ziggurat" on one of the first areas I generated - would consulting the oracle assist in populating spaces with stuff?
There are no specific rules to populate the different Areas within a Rift, aside from the Area's description and what you find. If you want more granularity you would have to use the oracles, yes. I considered adding that kind of stuff but the book was already enormous so I had to leave it out. At least for now...