The Super Eagles became the first African nation to qualify for the tournament, thanks to a 1-0 win over Zambia on Saturday, at the Godswill Akpabio Stadium in Uyo.
“It was a very difficult game and we didn’t underrate this team because we saw on video what they did to Algeria two times and against Cameroon,” Rohr told media.
“We knew it would be a very tough game and they gave us a chase. We didn’t want to concede a goal and we were lucky to get the goal which took us to Russia.
“Starting with Simon Moses and bringing in Alex Iwobi was not easy for us but that made the difference.
“In five games, we have four victories and one draw – a result I didn’t believe because of the teams in this group.
“It is not finished because the most difficult will be to prepare for a good outing at the World Cup.”