The 32-year-old soloed clear of the peloton with just over a quarter of the 120km race remaining.
“I'm so proud of our team,” an elated Hosking said afterwards. “The girls really rose to the occasion today and rode like they were protecting the yellow jersey.
“I've been struggling in the last few races so while third isn't the victory we had hoped for I can definitely take some kind of confidence from it going into the next two days.”
Emma Johansson has joined the black and orange team at the number one spot in the UCI Rankings after some spectacular results this spring.
The former two-time road World Champion crossed the line well clear of her nearest rival.