For example, you are long/buy a crude oil futures contract in March at the spot price of $100 which expires in June. Then the day before they expire, the spot price of the June contract is $70.

If you offset the position, you will have to sell the contract which makes you lose $30. If you rollover, you will sell the June contract and buy a July contract. Does it mean that you also lose $30 when you rollover? If right, then what differences between these two options since they have the same loss?