PARIS — You can find the genesis of the new Rick Owens show in the 1888 painting “The Roses of Heliogabalus” by Sir Lawrence Alma-Tadema. It depicts an event notorious in ancient history, when the young Roman emperor Heliogabalus suffocated the guests at one of his banquets with tons of rose petals. Rose petals have been on Owens’s mind for a while. “But I didn’t have enough of them to kill everybody,” he said before his show on…