According to manager Joe Girardi, Roberts will be the everyday starter and Kelly Johnson will serve as the backup. Johnson will likely split his time at second and third base, as well as the outfield. If (or when) Roberts gets hurt, look for Johnson to become the starter.
When healthy, Roberts has been a productive player throughout his career. He owns a career .278/.349/.412 line and has always been solid defensively; it's just going to be a matter of the veteran second baseman avoiding the disabled list in 2014.
Fortunately for the Yankees, they have suitable backup options on the bench. Johnson is a career .253/.335/.427 hitter and has upwards of 16 homer runs in each of the last four seasons. Eduardo Nunez could also see an increased role at second or third should injuries arise.