A digital EP featuring Jessica , Tiffany , and Seohyun was released on April 2008 , titled Roommate . During the group 's promotions , members Jessica , Tiffany and Seohyun were also featured on a mini-album released by Roommate , a one-man band from Purple Communication . The mini-album was titled Roommate : Emotional Band Aid , and was released on December 1 , 2008 .