Roozendaal was campaign director for Premier Bob Carr's successful election campaign in 2003. He was also the party's chief fund-raiser, raising a reported $16.3 million in his four years as General Secretary. He also carried out a crackdown on branch stacking and insisted on the selection of more female candidates in safe Labor seats.
Roozendaal was also Labor's New South Wales campaign manager at the 2004 federal election, but was widely reported to have a poor relationship with the then party leader, Mark Latham, and also with Latham's predecessor and close supporter, Simon Crean. It was reported that Roozendaal was a consistent ally of Kim Beazley and supported his claims to the leadership both in 2003 when Crean resigned and again in 2005 when Latham resigned.
As Roads Minister, Roozendaal was embarrassed for being caught illegally travelling in a Sydney bus lane in his motor vehicle, and for dumping a promise to widen the problematic Spit Bridge just two months after the State election. He was also against cyclists using roads during busy times, saying it was "not helpful" for cyclists to ride in peak hour traffic.
Despite these criticisms, Roozendaal was promoted to Treasurer by incoming Premier Nathan Rees, with immediate responsibilities for producing a 2008 mini-budget and maintaining the State's credit rating.
Roozendaal has described himself as a "rev head", due to his love of V8 Supercars. He was an advocate for transforming Sydney Olympic Park into a V8 Supercar circuit.