“Some rednecks are coming to town and taking over,” joked Rascal Flatts’ Jay DeMarcus midway through the opening-night show of the trio’s nine-concert residency, dubbed Rascal Flatts Vegas Riot!, at the Hard Rock Hotel in Las Vegas. It’s the first extended stint by a country act at the casino’s 4,000-seat theater, The Joint, which has hosted past residencies by acts like Def Leppard and Mtley Cre.