Rösler wuxuu ku biiray FDP iyo ururka dhallinyarada siyaasadeed ee dhalinyarada ah, ee dhalinyarada ah, 1992. Wuxuu ahaa xoghayaha FDP ee gobolka Lower Saxony laga bilaabo 2000 ilaa 2004 wuxuuna u adeegay guddoomiyaha kooxda baarlamaanka FDP ee golaha gobolka Lower Saxony laga bilaabo 2003. Laga soo bilaabo 2001 ilaa 2006, Rösler wuxuu xubin ka ahaa golaha gobolka ee Hannover (deegaanka), halkaas oo uu sidoo kale ahaa ku xigeenka guddoomiyaha kooxda baarlamaanka. Bishii Maajo 2005, waxaa loo doortay kormeeraha guddiga fulinta ee FDP. Wuxuu helay 95% codadka, natiijada ugu wanaagsan ee shirweynaha xisbigaas. Shirweynaha xisbiga ee gobolka Maarso 2006, Rösler waxaa loo doortay guddoomiyaha FDP Lower Saxony isagoo helay 96.4% codadka; wuxuu ku guuleystey Walter Hirche, oo ka tagay hoggaanka laba iyo toban sano ka dib. Bishii Abriil 2008, Rösler waxaa loo xaqiijiyay inuu yahay guddoomiyaha xisbiga FDP ee dhalinyarada Saxony
Sannadkii 1992