I'm almost positive the correct term is roller marks not lines but that's what I've heard them called the most so yeah, I ran with it, lol.
I have some idea of how metal stock is rolled into flat bars and strips from which coin planchets are punched. It is easy to see how such lines or marks could occur, although I am not sure just how they happen. Most of the flat stock comes out pretty smooth. Maybe I need to watch more youtube videos and learn more. Actually, it would be a great learning experience to go work at such a factory, also at a mint.
There's not a whole lot of info out there about it other than the striking process is supposed to smooth out the lines but doesn't always for some reason and that there is no added value for roller marks. Tho I've seen people try to sell "roller mark mint error Woody's" for a ridiculous amount, lol.
I searched online and found nearly nothing about roller marks or lines. Did find some about woodies and some articles claiming it to be a type of error and much more valuable even though being a normal business strike. I just like them because they look neat. I would choose a woodie rather than a chocolate brown anytime.