Roll crimp shotgun shells

[2eagles]

I've noticed Federal, and maybe others, is using a roll crimp on some of their shells. I remember the roll crimp from when I was a kid back in the 60's but it was disappearing in favor of the star crimp. First thought is the roll crimp is needed to keep in tiny shot and the buffer. I know I've melted candle wax on Hevi-shot shells to keep the buffer from leaking. Any other thoughts on the subject?

[Gooserbat]

Longbeards are roll crimped as well.  I load my own tss and there are ways to star crimp and not have a leak but a roll crimp is an easy fix.