Daryl Veltman had four goals for Calgary (4-10) while Jeff Shattler also scored three times. Curtis Dickson struck twice with Scott Carnegie and Sean Pollock rounding out the attack.
Adam Jones found the back of the net five times for the Mammoth (8-6), who snapped a four-game winning streak. Bob Snider had a pair of goals while John Grant and Eli McLaughlin also chipped in.
Frankie Scigliano made 25 saves for the win. Alex Buque turned away 39-of-51 shots in 59:58 for Colorado.
The Roughnecks went 3 for 6 on the power play with the Mammoth scoring twice on seven chances on the man advantage.