The Rousers, from Madison, Wisconsin, mix 50s rock and roll with traditional country to create raucous roadhouse music perfect for getting drunk to. While there's nothing all that new about their original material, it's performed with stirring conviction and the tightness that comes from doing years of three-sets-a-night club dates. Ernie DeMille's guitar playing is the real thing, by turns raunchy and sentimental; singer Frank Furillo has an emotive baritone especially effective on slower songs like "Why Don't They Write About Me?" which I predict here and now will become a country classic. Tonight, Biddy Mulligan's, 7644 N. Sheridan; 761-6532. Saturday, Gaspars, 3159 N. Southport; 871-6680.