Sometimes credited under the screen name Roy Haron, Horan was born in Laurel, Maryland. After graduating college he moved to Japan where he studied karate and shorinji kenpo before traveling to Taiwan to train in kung fu with Lawrence Tan, who introduced him to the film industry. Horan secured his first role in the 1977 movie Bruce Lee's Deadly Kung Fu. He'd go on to study taekwondo with Hong Kong actor Hwang Jang-Lee, with whom he'd make the popular martial arts instructional video, The Art of High Impact Kicking. Moving to Hong Kong, Horan appeared in additional films there, most notably the Jackie Chan movie, Snake in the Eagle's Shadow, Game of Death II and No Retreat, No Surrender II, the latter of which he co-wrote and produced.
Horan's daughter, Celina Jade, is also an actress having appeared in several martial arts films.