When you say You Rock to someone it means that you think that they are dependable, reliable and someone with a solid foundation.
It is informal English and is commonly used by the younger generation. It is also used to express admiration or appreciation for someone.
U2 is often used in short text messages to abbreviate the words “You too” but U2 is also the name of a famous Irish rock band formed back in 1976. They are still performing to this day and are one of the greatest rock bands of all time.
This is by no means the first cartoon on the subject but the idea popped into my head and the only way to get it out is to draw it.