This is pure speculation, but suppose the word 'roses' in the song is actually intended as 'Rose's', as in another woman, perhaps the one he refers to wedding in the previous line. In that case it would add quite a dose of sarcasm to the entire song's meaning, because it would be referencing 'Rose's dead flowers,' being his bride's dead wedding flowers that he'd be putting on (Susie's?) grave. Try thinking "Rose's" the next time you hear it.
This is pure speculation, but suppose the word 'roses' in the song is actually intended as 'Rose's', as in another woman, perhaps the one he refers to wedding in the previous line. In that case it would add quite a dose of sarcasm to the entire song's meaning, because it would be referencing 'Rose's dead flowers,' being his bride's dead wedding flowers that he'd be putting on (Susie's?) grave. Try thinking "Rose's" the next time you hear it.