Scientist and cultural observer — as well as Starfleet Academy dropout — Nikolai is the son of Sergey and Helena Rozhenko. Nikolai is also the adoptive brother to Worf. The two entered Starfleet Academy in 2357.
In 2370, Nikolai was assigned to Boraal II, where he acted as an observer. However, he overstepped his assigned duties, got involved with the welfare of the native Boraalans and eventually broke the Prime Directive in an effort to save their civilization.
Rozhenko fathered a child with Dobara, one of the Boraalans.