More of a side are roll cast than an overhead roll cast. It works well when you have overhanging trees, but not when you are up against the right bank of a tight stream. So you need to be able to roll cast overhead, to the dominant side, and to off side of your opposite shoulder.
Also he is using a longer SOFT rod, softer than almost all of us use for regular overhead casting. Look at 2:02 and go frame by frame. The fly rod bends down to the butt. That rod really works well for roll casting a long line. Regardless, he is a great caster and teacher.
"Discovery consists of seeing what everybody has seen and thinking what nobody has thought"..........Szent-Gyorgy