The skull represents death in most cultures, but quite as often it is used to symbolize vanity and its futility, the fact that in the end we will all be the same.

Adding flowers to it usually represents the contrast between life and death and the fact that life will always triumph upon death.
In this case, roses symbolize love and how it will last beyond earthly separation.

This design is part of a "Day of the Dead" mini series which can be found clicking on this link