Alex Newhook and Cale Makar scored in regulation for the Avalanche, who have won seven of their last eight games and moved within a point of first-place Dallas in the Central Division. Alexandar Georgiev made 22 saves for the Avs.
Rantanen beat Oettinger to the glove side on the second of Colorado’s three shootout attempts.
Robertson sent the game into overtime with a 6-on-5 goal from a tough angle at the top of the right circle.
Newhook was alone in front of the crease to cash in on a rebound after Oettinger made a point-blank save on Evan Rodrigues to give the Avalanche a 2-1 at 2:06 of the third period.
Robertson’s first goal, at 5:33 of the second period, tied the score at 1 and was awarded after a lengthy review. Robertson poked at the puck as he was being cross-checked by Andreas Englund head-first into Georgiev, with the resulting collision knocking off the net after the puck crossed the goal line.
Robertson has 14 goals, tied for second in the NHL. Twelve have come during his current 12-game point streak, which is one game short of the all-time Dallas mark set by Dave Gagner in 1993-94.
Makar opened the scoring with a power-play goal at 10:10, a one-timer into the top corner off a pass from Rantanen behind the net. That gave the league’s best power play going into the game (36.5%) a man-advantage goal in six consecutive games.
The goal gave Makar, in his fourth season, 200 career points. He’s the fastest NHL defenseman to reach that milestone, doing it in 195 games. That’s 12 games faster than Sergei Zubov, whose uniform number was retired by Dallas.
Avalanche: Host Vancouver on Wednesday
Stars: Host Chicago on Wednesday.
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The Associated Press