Kalu, yet to represent the country at any level, swapped Gent for the former Ligue 1 champions in a five-year deal , after dazzling displays since joining the Ghelamco Arena outfit from AS Trencin in January 2016.
And Rohr revealed the reason he overlooked the 20-year-old in the past was due to having a 'better' option in his former Gent teammate, Moses Simon - who also had Levante swoop for his signature.
However, with Kalu's high-profile move to France, the Super Eagles boss will consider having him in his plans.
“I never selected him. I saw him play, but in his team. I took another, which is Simon Moses. He is in my group since the beginning, two years ago. He is also a winger, fast. He’s almost the same, but I found him better than Kalu,” Rohr told Girondins4ever .
“We have many fast wingers in Nigeria. Before there is a plethora of quality attackers. This boy [Samuel Kalu] could not join our selection. But now, maybe he's going to cross a course. We'll follow him.
“Simon Moses was in my group. He was injured, he is the only injured player I had before the World Cup. He missed the World Cup because of a muscle injury. He was replaced by another player, a centre forward."
The German tactician concluded by highlighting some of the proven qualities Kalu will add to Gus Poyet’s setup.
“Samuel Kalu goes fast, he's a good dribbler, and he's an overflowing winger. He's explosive, he gives a lot of good balls, centers.
"He overflows, he can play on both sides. I hope Bordeaux will have the satisfaction of seeing him evolve with these qualities.”
On September 7, the Super Eagles look to get their Afcon 2019 qualifying campaign back on track as they host Seychelles.