A celebrity roast is usually fun for the audience, but far less so for the subject of the mockery. According to the finale of Feud, Bette Davis regretted the roast she participated in through The Dean Martin Show. While the FX series depicts The Dean Martin Celebrity Roast as fairly cruel, you can watch Davis' 1973 roast on YouTube and see for yourself.
In the Feud: Bette and Joan finale, Crawford seems to hit a lower low than Davis in her career, but the roast is portrayed as definitely not a high point for Davis. Dominic Burgess' Victor Buono calls the roast "the cruelest of degradations, demeaned and insulted by fifth-rate celebrities." The roast aired in October 1973 and was hosted by Martin, who had retooled his show that year to follow the format of the New York Friars Club roasts and continued to be a roast master until 1984.
As Feud shows, the roast, which aired in October 1973, featured Martin, gossip columnist Joyce Haber and actor Vincent Price. However, it also included Pat Buttram, Kay Medford, Nipsey Russell, Army Archerd, Barbara Heller, Howard Cosell, and fellow famous actor Henry Fonda, who starred in Jezebel with Davis in 1938. The roast, which you can watch in full below, also included a rebuttal from Davis, something that isn't shown on Feud, and did feature plenty of jokes about Davis' rival Crawford. (Before embarking, be prepared from some politically incorrect and racist jokes.)
Although Feud shows Davis as not enjoying the roast and Buono saying she regretted it, I didn't find any evidence of that. I personally get the vibe that the actual roast was more well-intentioned than Feud shows. After all, Martin had roasted other big names like Ronald Reagan, Hugh Hefner, Ed McMahon, and Kirk Douglas before Davis, so she was in good company. And I certainly wouldn't consider Fonda a "fifth-rate" celebrity as Buono notes. Plus, Davis returned to Martin's dais to roast Johnny Carson.
Roasts at their core are insulting as a form of flattery — and sometimes respect. Perhaps Davis' roast was a testament to her legacy as one of the greatest actresses to ever live. Or maybe it was, as Feud suggests, a cruel joke on an aging actress that Hollywood didn't want anymore. Either way, Davis seems to have gotten the last laugh as she is still a highly-regarded actress all these years later.