Beverly Hills-based Concord Music Group has acquired Boston-based roots music label Rounder Records. Terms of the purchase were not revealed.Rounder, which is currently celebrating its 40th anniversary, issued one of the biggest roots releases of recent years, Robert Plant and Alison Krauss’ “Raising Sand,” winner of the album of the year Grammy in 2009. Its 3,000-title catalog covers the breadth of American roots music; labels acts include Krauss, country luminary Willie Nelson, banjo iconoclast Bela Fleck and chanteuse Madeleine Peyroux, among others. Acquisition adds further heft to Concord’s formidable catalog of 10,000 titles. In 2004, the company, owned by Norman Lear, acquired Berkeley-based Fantasy Records, which controls the Creedence Clearwater Revival catalog and such invaluable jazz and R&B imprints as Prestige, Milestone, Riverside, Stax and Specialty. Both Concord and Rounder are distributed by Universal Music Group.