Thyme is definitely virginity and rose refers to the sores of a STI, although some of the romantics amongst us (me!) like to think he actually gave her a beautiful rose from a proper garden and it lives forever.

In one version of Streets of Laredo roses are used to cover the coffin to stop the smell from the body of a young cowboy who died from a STD. In another version of the same song roses are used on top of the coffin to deaden the sound of the clumps of earth as they are thrown on the coffin in the grave.