You can normally tell if the trade is a rollover by the same quantity being sold and bought back and a very narrow spread like 0.02 and within 30 seconds of each trade
A rollover is when you purchase a stock on a extended settlement (T20) so if you bought 100k IMM today on a T20 you would be able to keep it for 20 working days or a month without paying for it. If you don’t close the trade on or before the 18th day you would have to pay for it on the 30th day (T18+2) but then you could rollover the position for another month like those trades this morning.