VIDEO : What is One of the Biggest Lessons Rose Byrne Has Learned Since Becoming a Mother

Even stars of Rose Byrne 's caliber have to follow the rules. In February, the 36-year-old actress welcomed her first son, Rocco , with her 46-year-old partner, actor Bobby Cannavale . In the last few weeks, Rose has been traveling all over the country to promote Universal Pictures' Neighbors 2: Sorority Rising and 20th Century Fox's X-Men: Apocalypse , and on Thursday, she stopped by CBS' The Late Show With Stephen Colbert in New York City. It was on that very show that Bobby announced Rocco's birth .