The well in PSC Area B is the second of two wells to be drilled by Petronas after it acquired Woodside Petroleum's Mauritanian assets in September last year.
The Banda discovery well drilled in 2002 encountered a 110m gross gas column and a 10-20m gross oil column.
The earlier Khop-1 exploration well in PSC Area C Block 6 was plugged and abandoned after encountering thin sands with non-commercial oil shows.
Roc has a 3.69% stake in PSC Area B and a 5% stake in PSC Area C, Block 6.