Investors look at past returns when buying a mutual fund. Fund houses always disclose point to point returns which just tells you what happened between those dates. But it does not capture the fluctuation in NAV values. A rolling return, therefore, better captures how the fund has performed over a time period. More importantly, it reflects how consistent the returns have been. For example, for a 5-year rolling return, you see returns of March 20,2023 vs March 20,2019 as one data point, then March 19, 2023 vs March 19,2019, as the second data point and so on till March 21, 2019's returns versus March 21, 2015's. It shows how a fund delivered under different market conditions.