Madras High Court Chief Justice M Y Eqbal administered the oath of office to Rosaiah at a function in Raj Bhavan in Chennai. He succeeds Surjit Singh Barnala.
The brief function was attended by Chief Minister J Jayalalithaa and her cabinet colleagues among others.
Soon after he was sworn-in, Jayalalithaa and Justice Eqbal presented bouquets to him.
78-year old Rosaiah, a veteran Congress leader of Andhra Pradesh, brings with him a vast political and ministerial experience having served as Chief Minister from September 3, 2009, to November 24, 2010, besides being a minister in successive Congress governments in the state since 1979.
Rosaiah became Chief Minister following the death of Y S Rajasekhara Reddy in a helicopter crash. After tumultuous 14 months as CM during which he faced the twin challenges posed by Telanagana movement and the then dissident leader Y S Jaganmohan Reddy, he quit the top post on health grounds paving the way for incumbent Kiran Kumar Reddy.
Born in a middle class agricultural family at Vemuru in Guntur district on July 4, 1933, Rosaiah did graduation in Commerce and was active in politics since his student days.
Belonging to Vaishya community, he was first elected to AP Legislative Council in 1968 and became a minister in 1979 under late M Channa Reddy who incidentally was Tamil Nadu Governor during AIADMK's first government in 1991-96.
Rosaiah, initiated into politics by veteran freedom fighter late N G Ranga, is the 22nd Governor of Tamil Nadu.
Later, Chief Justice Eqbal and Jayalalithaa introduced the Judges of the Madras High Court and state cabinet Ministers, respectively, to Rosaiah.
Several well-known personalities from Andhra Pradesh including actor-politician Chiranjeevi, industrialist Subbiramy Reddy and many others were present at the swearing-in ceremony.