Entertainment Weekly featured an article about Hot Rod in one of their latest issues, and has this weekend also made that content available online. The article talks in some detail about Hot Rod and at least his initial role in the movie - explaining the context for the detailed image we saw recently. A little comes out about Laura Haddock's character and her importance as well. All of this is a bit spoiler-leaning, but if you're okay with that, you can find select excerpts below!
Hot Rod has secretly been serving as her protector in the guise of her father’s 1963 Citroën DS.
Also at the time the EW article was written, it seems casting for Hot Rod was still in progress. Reference is made to not having a voice selected, while audiences for the sizzle reel preview event did in fact hear Hot Rod speaking with a French accent. Lorenzo di Bonaventura is also quoted as saying that "a lot of the robots are not being voiced", so outside the principle cast, perhaps don't expect to be hearing many new characters to speak up.