As with anything WIS has Roll Over down to a fine art and is somewhat complicated but follows these rules.
1. Roll Over occurs 1 hour before any cycle update, plus or minus a few minutes.
2. Eligibility for Roll Over is the cycle immediately following the World Series. If the WS ends on AM Cycle part 1 a World is eligible for Roll Over 1 hour before the AM Cycle Part 2 on the scheduled Roll Over day.
3. Order for Roll Over, if multiple Worlds have their WS end on the same cycle it defaults to the World number. Simply put a Season 15 World is before a Season 14 World, if both are Season 15 then the World with the lowest World Number goes first. However Worlds that are scheduled for the previous day and has yet to Roll Over has first priority.
After examining our situation, 3 Worlds are scheduled to Roll Over after the PM2 Cycle 1 update the previous day to ours. One will Roll at 10pm EST, the second will roll at 2AM EST on the 18th, the 3rd will Roll at 6AM EST. That leaves us with the 10AM EST slot. Or at least this is how I remember it working.
Then again, a World may not be eligible for Roll Over until after the cycle part 2 update after the the World Series. Have no clue as to why we didn't roll at 2pm or 6pm, another world did and shouldn't have.