I have the book written by Thomas Poffenberger "From Germany to Antietam" He does mention Rosannah and her parents.
First he mentions that Rosannah was married twice. First to John Holland then to Jacob Slaymaker. He does not say where she was born. He says she was born about 1802. Here is what he has about her parents: John Poffenberger was born about 1762. and died about 1840. He married Maria Magdeline by 1786. He was listed in the 1790 census in Washington Co, Md near his Simon and Christian and near his father John. The 1800 census has him in Sharpsburg Hundred.His will states that he owns 706 acres in Virginia. What records exist were taken from the Frederick Co courthouse eleven children (seven sons) and gives information on four of them. There were three early Hollands in Frederick Co. Capewell Holland,Captain and Thomas Holland. I have no information about them. Try familysearch.com for more. He then lists all the sons and tells about them. He gives very little about the daughters. All there is about Rosannah is listed above. I hope this helps. You can likely get a copy of the will from the Frederick Co clerk at the courthouse. They are very helpful there.