The role of starch in iodometric titrations is that

In iodometric solutions, I2 solution to be estimated is pippetted out is conical flask to which starch is added as indicator blue colour develops.Now the standand solution of Na2S2O3 taken in buerette is added slowly to the contents of the conical flask. Na2S2O3 reduces I2 to I- due to which blue colour disappears