Daisy Pearce's Eagles were dealt a massive blow just hours before Saturday's clash at Henson Park after main ball-winner Roberts was ruled out with hamstring tightness.
Eagles defender Annabel Johnson came into the side as the Swans posted a 6.7 (43) to 3.8 (26) victory in front of 4519 fans.
Sydney can finish the penultimate home-and-away round in eighth as one of four teams on 24 points, while West Coast - chasing their maiden finals berth - remain sixth on percentage.
Eagles coach Pearce is confident Roberts will return against fellow finals hopeful Carlton on Friday night.
"She was close and a bit disappointed when we made the call for her," Pearce said.
"She's a competitor who wants to be out there, and I doubt it's gotten any better now, but nah, she'll be attacking next week."
But coach Scott Gowans will be sweating the fitness of Cynthia Hamilton after the star forward hurt her left ankle in a front-on collision with Eagles players Sanne Bakker early in the first term.
Hamilton lay on the ground in agony and required assistance to leave the field, before being substituted out of the game at quarter-time.
"She (Hamilton) was just saying then, she's a bit sore right up her leg so whether that's nerves or anything, we're not sure," Gowans said.
The home side were also without star duo Chloe Molloy (back) and Sofia Hurley (quad), but it mattered little as Privitelli made the most of her recall to the side.
Privitelli pulled off her goal haul from just nine touches to remind Gowans of her quality.
The 30-year-old had been missing from the side for three weeks, with Saturday's clash just her fourth game this season.
Laura Gardiner (30 disposals) saw plenty of the ball in her 50th game, well-supported by fellow Swans midfielder Tanya Kennedy (seven clearances).
Lauren Wakfer was among West Coast's best with one goal, 14 disposals and four clearances.
Sydney rallied quickly after losing Hamilton, with Privitelli opening the scoring with her first goal of the season to help set up an eight-point lead at quarter-time.
West Coast could only cut the deficit to four points in the second quarter as both sides struggled to hit the scoreboard, slotting one goal each.
The home side finally broke away when Privitelli kicked her third goal of the match, taking a 23-point lead at the final break.
Kellie Gibson kicked off the final term with West Coast's first goal since the second quarter, but she couldn't spark a comeback.
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