Starting his career as a child, he has appeared in many television series. His credits include: Knots Landing, The Greatest American Hero, St. Elsewhere, Manimal, The Love Boat, Highway to Heaven, Murder, She Wrote, Diff'rent Strokes, T.J. Hooker, The A-Team, Cagney and Lacey, Hill Street Blues, The Wonder Years, Jake and the Fatman, Baywatch and Tremors (TV series) .
He also supplied the voice of Dorin in the animated television series Wildfire.
In addition to acting, Robert played Black Jack professionally with a team of well known card counters from 2000-2005 . In the 2010 Penguin Publishing offering of "Repeat until Rich", Josh Axelrad describes his experiences in Las Vegas with Robert Jayne and a team of world famous card counters as they use "Big Player" and "Call-in" tactics to win millions of dollars. Robert became a well known player and was entered into a "Black List" by the Griffin Agency, known for supplying intelligence information to casinos regarding players that can "hurt" the casino by winning money. Link:Griffin Agency
He played in the first ever "World Series Of Black Jack" against such notables Stanford Wong and Hollywood Dave under the name "Bobby J".  It pitted some of the best and well known Black Jack players from around the world.
He is the brother of Scott Jacoby, Billy Jayne, Susan Jayne, and Laura Jayne. All of them participated in film and television projects, with Scott Jacoby winning an Emmy for the television movie "That Certain Summer".