Rosalee Calvert is a Fuchsbau. She is an extremely kind and loving person willing to do whatever it takes for her friends. She is the sister of Freddie, proprietor of the herb shop used as a front for the Geier organ trafficking business. After Freddie's death, Rosalee comes to Portland to sort out her brother's affairs and decides to stick around.

Prior to her arrival in Portland she spent her earlier years trying to follow up her parents' profession as an apothecary, but didn't like the job, in spite of her aptitude for it. She became hooked on a highly-addictive Wesen-oriented drug street-named 'Jay' and left Portland to get clean. After deciding to keep her brother's shop running, Rosalee assists Nick and Monroe in their efforts by providing additional information and remedies to supernatural problems.

Rosalee shares a powerful connection with Monroe. They go on their first date and share their first kiss, after which Rosalee uncharacteristically attempts to seduce Monroe. This seduction attempt turns out to be the manifestation of a common symptom from the Wesen virus Rosalee had been exposed to during their date. After being cured, Rosalee and Monroe agree that the attraction between them was real, but decide to take it slow before becoming intimate with each other.