Answer
Fortuna Düsseldorf was the team managed by Rösler before he joined AGF. Rösler had a successful stint with Fortuna Düsseldorf, leading them to promotion to the Bundesliga in 2018 and guiding them to a respectable 10th-place finish in the following season. His impressive performance at Fortuna Düsseldorf earned him the opportunity to manage AGF in 2020.