This phrase, made popular by the nu-metal band Nickelback, can mean one of two things, both however have the same underlying meaning.
1. A phrase almost always used sarcastically to denote how much something sucks
2. A phrase used to denote something good, but also used sarcastically because Nickelback really does suck
1. Andrew: "Man we just lost that game 86 to 53."
Jim: "Yeah that really Rocks Like Nickelback."
2. Paul: "Dude I just got the goods."
Time: "Man that Rocks Like Nickelback."