What It Means
Rollover means closing a futures or options position in the current expiry and simultaneously opening the same (or similar) position in the next expiry, to keep the trade running without letting it get auto-settled.
How It Works
Traders roll over positions they want to hold beyond the current expiry — often visible in the days leading up to expiry as "rollover data," which analysts watch as a sentiment signal (heavy rollover at a bullish cost-of-carry suggests traders expect the uptrend to continue, and vice versa). Rolling isn't free: it means paying the bid-ask spread and brokerage twice (exiting the near contract, entering the far one), plus the price difference between the two expiries, called the cost of carry. For index futures, that cost is usually small and predictable; for stock futures around events like earnings, the rollover cost can widen noticeably.