A person that is born a hermaphrodite and chooses the male sex due to the inability to grow breasts. Given a name that is interchangeable between the male and female sexes in order to allow for a gender decision. After a choosing a gender, this person tends to sexually attract members of both sexes.
"He's so girly, I wonder if he's gay."
"No, he's not gay, he's a rosenberg."
When somebody successfully urinates on a males ballsack.
Myles: "Pissing on ballsack"
Taylor: NOOO! Nigga gave me a rosenberg!