The Eagles kicked three goals to nil in the first quarter of Saturday's match as Roberts ran amok in front of 2470 fans at Mineral Resources Park.
But Port, led by Gemma Houghton, turned the tables from that point on, kicking the next five goals to secure the 7.7 (49) to 5.6 (36) victory.
Although West Coast (4-3) are still clinging to seventh spot, they face tough fixtures against top-four fancies Hawthorn and Fremantle in a two-week stretch that will make or break their season.
Port Adelaide's second win on the trot improved their record to 3-4 and moved them into eighth spot.
More importantly, their final four games - against Collingwood, St Kilda, Gold Coast and GWS - are all against teams currently outside the top eight.
Abbey Dowrick starred for Port with 19 disposals, eight clearances and 546m gained, while ruck Matilda Scholz gave her team the edge in the midfield battle with 23 hit-outs and six clearances from 15 disposals.
Houghton finished with 2.2 and four tackles in a standout display.
A hot start to the final term from Port 😤— AFL Women's (@aflwomens) #AFLWEaglesPower pic.twitter.com/TYkxdv71LUOctober 5, 2024
"That was incredible. I'm so proud of the girls," Houghton told Fox Sports.
"West Coast came out really hard, and for us to bounce back and get that win, I'm so proud of that."
For West Coast, Roberts finished with 27 disposals, 11 marks and a goal, while Bella Lewis was also influential with 26 possessions.
It was the Roberts show in the first quarter as the star midfielder took a remarkable four contested marks to go with her 11 disposals and 214m gained.
The 19-year-old also kicked a goal and set up another, with her hot form helping the Eagles build a 19-0 lead by quarter-time.
Port clamped down on Roberts in the second quarter via a hard tag from Shineah Goody, and the move paid dividends as the visitors turned the tables to take a one-point lead into half-time.
Ella Roberts (centre) stood tall for the Eagles in their AFLW clash against Port Adelaide in Perth. (Richard Wainwright/AAP PHOTOS)
The Power won the inside-50 count 16-1 for the term, with Houghton snapping her team's first goal as Port put the Eagles under all sorts of pressure.
West Coast's Zoe Wakfer gave away a silly 50m penalty when she rolled the ball back to her opponent instead of throwing it back on the full, with the brain fade costing her team a goal.
Justine Mules-Robinson, in her 75th game, kicked two goals in the space of a minute early in the third quarter as Port's lead swelled to 14 points.
A goal to West Coast utility Abbygail Bushby after the three-quarter-time siren gave the Eagles a sniff, but Houghton snuffed it out early in the last term by kicking a goal and setting up another.
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