Roscoff is a commune in the Finistère département of Brittany in northwestern France. Roscoff is renowned for its picturesque archite…Roscoff is a commune in the Finistère département of Brittany in northwestern France. Roscoff is renowned for its picturesque architecture, labelled petite cité de caractère de Bretagne since 2009. Roscoff is also a traditional departure point for Onion Johnnies.