The original "roses are red" poem can be traced back to the 19th century. When the post office started in Britian, people started to send Valentine’s cards to the person they loved on the 14th of February. The cards had pictures of flowers and birds on the front and words inside like:

Roses are red, my love
violets are blue,
Sugar is sweet, my love
but not as sweet as you.

The modernized version that most people today know is:

Roses are red
violets are blue
sugar is sweet
and so are you