Simplify the following text for a Grade 5 native English-speaking person.
Original: Rosberg won the 2005 GP2 Series for the ART team , having raced in Formula Three Euroseries previously for his father 's team .
Simplified: Rosberg won the 2005 GP2 Series for the ART team . Before that , he raced in Formula Three Euroseries for his father 's team .