
Quick answer — Yoriko Nagata voices Nobuyo Nakajima in K-ON! Season 2, Fumie Kimura in K-ON!, Jun Suzuki in K-ON! and 7 more characters.
Yoriko Nagata voices Nobuyo Nakajima (K-ON! Season 2), Fumie Kimura (K-ON!), Jun Suzuki (K-ON!), Rika (Polar Bear's Café), Sasha (Darker than Black: Gemini of the Meteor), Mikki (Ground Control to Psychoelectric Girl), Jaune Clafoutis (Dog Days Season 2), Jun (Katte ni Kaizou) and 2 more.
Nobuyo Nakajima is voiced in Japanese by Yoriko Nagata.