River City Roots isn’t quarantined to a single park or block. Instead, it spreads through a big chunk of downtown, taking over multiple blocks of Main and Ryman streets, incorporating a family-centric festival in Caras Park and including a 4-mile run across downtown. There’s art, food and, most importantly, music. Last year, Railroad Earth and the Gourds headlined the evening sets. This year, Sam Bush and Nathan & the Zydeco Cha-Chas will take top billing, so mark your calendar now for the weekend of Aug. 23 and 24.