What Is the Difference between ‘Roll Yield’ and ‘Carry Cost’ in Futures?

Carry cost is the expense associated with holding the underlying asset, such as storage fees and interest. Roll yield is the profit or loss generated when a futures position is 'rolled over' ▴ closing the expiring contract and opening a new one further out.

In a Contango market, rolling over results in a negative roll yield (a loss); in Backwardation, it results in a positive roll yield (a gain).