Having lost their opening Group J clash to South Korea on penalties earlier in the week Team GB knew that the Romania clash was a must-win encounter if they wanted to stand any chance of topping their group.
And goals from Leigh Jamieson, Ben O'Connor and Robert Dowd proved enough to secure the crucial victory.
Jamieson and O'Connor struck in the first period while Dowd wrapped up the win seven minutes from time, goaltender Stephen Murphy marked his 50th cap with a 17-shot shut-out as well.
And head coach Tony Hand admitted afterwards that his side were good value for the win.
"We dominated the game and fully deserved our victory," he said.
"All the guys played their hearts out. They were fantastic and there were man-of-the-match performances all over the ice.
"We are very much alive in this tournament and hopefully this result has set up a thrilling final game against Japan."
Hand’s side will take on the hosts on Sunday needing a win and if they top the group they will then travel to Germany in February for final qualifying for the Sochi 2014 Winter Olympics.