Words at Play : Top 10 Words from Trademarks, Vol. 2
The generic term is "in-line skates," but many people refer to them by the trademark Rollerblades.
In-line skates are actually the oldest kind of roller skates, dating back to the late 1700s.
In the late 1800s a version of roller skates with two parallel sets of wheels (sometimes called "quads") allowed skaters to turn and maneuver easily, and launched a roller skating craze in the U.S. and Western Europe.
In the 1980s hockey-playing brothers Scott and Brennan Olson brought back in-line skating by developing (and trademarking) Rollerblade.