At both of Obama's swearings-in (the first of which Roberts famously flubbed), he ended with a question, "So help you god?" Same just now for Biden.
Four long years ago, Roberts uttered the above line correctly, as a statement to be repeated, not as a question to be answered.
On 1/20/25 , before Biden (or Harris, if Joe decides not to run) takes the oath, s/he (or a spokesperson) should politely advise the CJ of the proper way to end the oath. (If he did that to me I would just throw the question right back at him, followed by, "Hey, I just repeated what you said, chief." )