Rottem was born on the island of Hemnskjela in what was then Heim Municipality.
His parents were Sverre Bernhardsen Rottem and Solveig Terese Hassel.
He was married to Gerd Synnøve Vigeland from 1969 to 1989, and to Bente Findling-Nielsen from 1991.
[1] He published several academic works about Knut Hamsun, and a biography of Sigurd Hoel (1991).
Norske forfattere i Kongens by (2000), Sild & snaps i København (2003), and Til bords i Tivoli (2004).