One of the last weddings performed in public in Las Vegas was on St. Patrick’s Day. The groom wore a dark suit. The bride wore a rockabilly-style black halter dress. The minister was Slash from Guns N’ Roses — or, rather, a licensed officiant performing as the shaggy-maned, top-hatted guitarist. As ceremonies go at the Rock & Roll Wedding Chapel in the Rio Hotel & Casino, it was fairly traditional.