This commentary will serve as an introduction to the dollar roll market. We start by defining the market’s protocols and terms, and address how lenders and investors each utilize the market. We then discuss the economics of roll transactions, with a detailed analysis of how values are calculated and how to use the roll calculator in Thomson Reuters Eikon. We also address how carry on MBS is calculated, as certain types of transactions are valued in a similar fashion to rolls. We conclude with a discussion of the technical factors impacting roll levels.