The roll cast has many uses but it’s main one is allowing us to make a cast when there is limited room behind us. We try to create a D loop of fly line behind (using the rod as the stem and the line as the curve of the letter D) and an anchor of line in the water in front.
By pulling this D loop of line forward against the resistance of the anchor, we are able to load the rod sufficiently to cast our fly. See video below for real time example and the picture for D loop set up. I have about 20 feet of line and a nine foot leader outside the rod tip.
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