is rolling skating(the old school style with 2 wheels on either sides) more towards a 70's trend or 80's?

It was really big in the 1970's around 77 and 78 when the fad was known as "roller Disco" At that time Macy's, Bloomingdales, and all the big high end department stores had "roller disco" departments selling sequined tube tops, stretch pants in shiny nylon spandex, and long tunic tops made from metallic threads. It was also a big fad in the late fifties early sixties, right at the beginning of rock and roll music. By the 80's roller skating was mostly over and roller discos were closing up.

Here's Gloria Gaynor's video for i will survive. There's a girl in the full roller disco outfit in the video doing all the popular roller disco moves. http://www.youtube.com/watch?v=Xv6lHwWwO3w

70s for sure.

I believe it's called "rollerskating".
70's and before that. In 50's-60's very popular too.
In-line skating came in the late 80's.