Rollerblading is a name used for inline skating sports because of the large role that Rollerblade© USA played in making inline skating popular. Rollerblade© did not invent, design or manufacture the very first inline skates. But, the company was so successful in marketing inline skates and equipment that the term "rollerblading" was and still is used when referring to inline skating sports. Inline skates are often called "rollerblades" regardless of which company actually built them. The name "rollerblading" has become inline skating to most people, overshadowing other manufacturers and leaving out a lot of the history of roller and inline roller.
Inline skating or inline roller skating is the official name for "rollerblading" or "blading" sports and inline skates is the correct name for "rollerblades" manufactured by any other company. If you actually use Rollerblade© brand skates, then you are really Rollerblading, otherwise, the correct description is inline skating.