The movie is called Ninja Thunderbolt and came out in 1986. Here's the synopsis at IMDB: "The Ninja Empire has been run by an evil master and one member decides to leave the empire. The ex-Ninja wants a Hong Kong detective to track down the new leader and end his reign of terror."
Here's the intro, which features some deadly serious ninja talk, but no roller skates:
Yes, it's on sale at at Amazon.
*Previously: Modern day ninjas arrested before carrying out their plan of harassing drug dealers.