“Who gave you the position to judge when it’s ‘too soon’ for a person who has suffered the worst to be able to find happiness and companionship again?” Ms. Roman wrote in her blog post. “How long should a widow sit in isolation before you are comfortable enough to release them from their solitary confinement?”

Ms. Roman congratulated the couple on their engagement and said she was glad to see that Mr. Oswalt’s heart “had expanded.”

“I used that word intentionally,” she wrote. “I say expanded because that’s what widowed hearts do. They expand. One love isn’t moved out to make room for someone new. An addition is built.”

Ms. Sandberg, who has spoken often of her grief over the unexpected death of her husband, Dave Goldberg, in May 2015, also weighed in with a message of support for Mr. Oswalt and Ms. Salenger and praise for Ms. Roman’s piece.

“I laughed and cried a bit because what you are saying is so true,” she wrote on Facebook. “No one should judge another’s path — and everyone deserves to find love again.”

Mr. Oswalt, a stand-up comedian known for a string of roles on film and television, including the sitcom “The King of Queens,” has been very public about his struggle with grief after the death of his wife. In an interview with The New York Times last October, Mr. Oswalt said he would “never be at 100 percent again.”