From Christopher Marlowe's The Passionate Shepherd To His Love. This was published posthumously in 1599; Marlowe died in 1593.
Come live with me and be my love,
And we will all the pleasures prove
That valleys, groves, hills, and fields,
Woods or steepy mountain yields.
And we will sit upon the rocks,
Seeing the shepherds feed their flocks,
By shallow rivers to whose falls
Melodious birds sing madrigals.
And I will make thee beds of roses
And a thousand fragrant posies,
A cap of flowers, and a kirtle
Embroidered all with leaves of myrtle;
A gown made of the finest wool
Which from our pretty lambs we pull;
Fair lined slippers for the cold,
With buckles of the purest gold;
A belt of straw and ivy buds,
With coral clasps and amber studs:
And if these pleasures may thee move,
Come live with me and be my love.
The shepherds' swains shall dance and sing
For thy delight each May morning:
If these delights thy mind may move,
Then live with me and be my love.
Here, Marlowe was referring to real flowers. The phrase has since come to be used figuratively to refer to any easy and pleasant situation - floral or otherwise. The literal interpretation of the phrase was taken up again in the imagery for the 1999 film 'American Beauty'. The commercial potential of that imagery was soon exploited and 'Bed of Roses' bath kits were soon on sale. They rather spoiled the effect by using the blurb 'if you want to re-create the inimitable scene from American Beauty...'.