Roy Orbison plus Jello Biafra equals Dex Romweber. Fans of the singer's famous former band, the Flat Duo Jets, know this already; they'd probably add Paul Westerberg to the equation. Whatever: Romweber is a great, great rock singer and guitar player whose intense, stripped-down roots-rockabilly sound is world famous. With his new band, the Dex Romweber Duo, he teams up with his sister, drummer Sara Romweber, who has played with Mitch Easter and Snatches of Pink. The new record, Ruins of Berlin, shows that these two rock-veteran siblings attack music with the energy of teenagers and the skill of hardworking superstars. Guests on the album include Romweber fans Chan Marshall, Exene Cervenka, and Neko Case not bad. The duo also makes an instore appearance at the Berkeley Amoeba today at 6 p.m.