So, I took over as commissioner of my league, and it says we're eligible for roll-over starting today. How do I do that? Is it automatic or do I have to do something. Thanks

It will rollover automatically.  I'm surprised it hasn't happened yet, as I thought worlds rolled 72 hours after the final World Series game (and assuming you're talking about The Show II, the last WS game was 10/11 AM, so I would have expected it to roll 10/14 AM).  Once it's full, you'll have to approve the league in order for it to start, but that should be about it.

There may be something else, as I've never been a commish, but I don't think so.

Worlds roll at specific times.  Nothing you can do to "push" the process.    The times are 6/10 AM and 6/10 PM.   Although I'm pretty sure I've seen three worlds roll in one day, the general rule is 2 per day.   One in the AM cycle, one in the PM cycle.  

Got it, thanks guys