The Islanders trailed only 2-1 in the third period before the Devils busted the game open.
Martin Brodeur made 22 saves for the Devils, who have won three straight and 11 of their last 14 games overall. Marion Biron made 36 saves for the Islanders, who have dropped four of six.
New York's only goal came from Richard Park, who put the Islanders up 1-0 at 11:18 of the first period. That goal stood up until Mottau scored 54 seconds into the second period when his centering pass deflected off a New York player's skate.
Rolston scored on the power play at 12:06 of the second period and then the Devils put the game away with three scores in a span of 2:02 in the third period and a final goal by Elias in the final minute.