Because they will already be in New York City with gigs on Saturday Night Live and The Colbert Report, Radiohead figured they might as well play a couple of concerts, too. They have announced two shows, on Sept. 28 and 29, at the Roseland Ballroom. Tickets will go on sale at 10 a.m. next Monday, Sept. 26 at Ticketmaster. There is a two-ticket limit per household. These shows are Radiohead’s first in the States since the release of The King of Limbs earlier this year.