The transaction with Brazil's Petrobas "nearly triples Statoil's production" in the nation, the company said in a statement.
The group already operates the Peregrino field and an oil block, both in the Campos Basin, and another block in the offshore Santos Basin.
"This transaction adds material and attractive long-term production to our international portfolio, further strengthening the position of Brazil as a core area for Statoil," president and chief executive officer Eldar Sætre said in the statement.
The energy giant, which is 67 percent owned by the Norwegian state, is increasing investments outside Norway to offset declining domestic production and disappointing surveys in the Arctic waters of the Barents Sea.
Active in oil development, production and exploration in Brazil, Statoil says it's "one of the largest producers of oil" in the country.
The Roncador field is the largest offshore oil field discovered in Brazil in the 1990s and is currently Petrobras' third largest oil field with reserves of 10 billion barrels of oil equivalent and recoverable reserves estimated at 1 billion.
In production since 1999, the Roncador field produced in November 240,000 barrels of oil per day and 40,000 barrels of oil equivalent per day of gas.