The company that started it all is a lot like the spandex-clad skaters who use its products--young, hip, and slightly unorthodox. Flocking to Rollerblade Inc.'s rallying cry "the asphalt is calling," one million Americans have strapped on in-line skates and hit the pavement. Another million will join them by yearend. Now, the question is: Can a company that has been skating on the fringe avoid falling on its face as it moves into the mainstream?