The couple revealed the news in the latest issue of In Touch Weekly via NYDN, where Hebert explained she was "a little nervous" but "very excited" about becoming a parent.
"I've wanted a child for a while," she said.
The couple explained that Hebert took a few home pregnancy tests that were inconclusive before getting the one that revealed they were about to become parents while the two were in California for Sean Lowe and Catherine Giudici's nuptials in January.
"There was legitimately a line," Rosenbaum said. "That's when we officially found out -- of course it would be at a Bachelor wedding!"
Hebbert and Rosenbaum met on the set of The Bachelorette during the show's 7th season. The two married in a televised ceremony in December 2012.
[In Touch via NYDN]