Zack Greer scored a hat trick and added an assist for Edmonton, while Matthew Dinsdale had a goal and three assists. Riley Loewen, Chris Corbeil and Ben McIntosh rounded out the scoring for the Rush, while Aaron Bold made 29 saves for the win.
The NLL divisional finals are a best-of-two series. If the series is tied after two games a mini-game will be held immediately after the conclusion of Game 2.
Curtis Dickson's three goals led Calgary and Dane Dobbie added a pair of goals. Shawn Evans scored and added four assists, with Curtis Manning and Daryl Veltman chipping in as well. Frankie Scigliano stopped 35 shots for the Roughnecks.
Edmonton went 3 for 6 on the power play and Calgary was 1 for 3 with the man advantage.