Please answer a question about the following article about House music:

It was during this decade that vocal house became firmly established, both in the underground and as part of the pop market, and labels such as Defected Records, Roule and Om were at the forefront of championing the emerging sound. In the mid-2000s, fusion genres such as electro house and fidget house emerged.[citation needed] This fusion is apparent in the crossover of musical styles by artists such as Dennis Ferrer and Booka Shade, with the former's production style having evolved from the New York soulful house scene and the latter's roots in techno.

Roule and Om was at the forefront of what type of house music?
vocal house