The film is scheduled to premiere on the cable network later this year.
"Sharktopus" is about a research scientist and his daughter who develop a secret military weapon -- a hybrid shark/octopus that can be controlled by electrical implants. But when the controls break down, the monster goes on a killing rampage at the resort beaches of Mexico, Syfy said in a news release.
Roberts received Golden Globe nominations for his starring roles in "King of the Gypsies" and "Star 80." He was nominated for the 1985 Academy Award for best supporting actor for his role as the escaped convict Buck in the film "Runaway Train." In 1987 he won the Theatre World Award for his Broadway debut performance in "Burn This."
His other film credits include "Raggedy Man," "The Pope of Greenwich Village," "Nobody's Fool," "Final Analysis," "A Guide to Recognizing Your Saints" and "The Dark Knight."