Philip Roth and Dick Cheney are unlikely bedfellows (just try expunging that image from your mind), but there are interesting parallels in both the style and substance of two documentaries devoted to them premiering this month: “Philip Roth: Unmasked,” which will make its debut at Film Forum in New York prior to a March 29 airing on PBS’ “American Masters;” and “The World According to Dick Cheney,” which Showtime will run March 15, following its premiere at the Sundance Film Festival.

In both projects, the filmmakers are content, essentially, to let the subject hold forth, without any ostensible follow-up questions or challenges. There are third-party voices — in Roth’s case, almost all fellow writers speaking of him with great admiration; and in Cheney’s, either associates like Donald Rumsfeld, or journalists who have covered him. (The Washington Post’s Bob Woodward calls him “One of the monumental figures in American politics.”)

Both men, moreover, speak about not giving a damn what other people think of them.

“I don’t spend a lot of time thinking about my faults,” says Cheney, when asked by co-director R.J. Cutler to discuss his, sounding completely unrepentant, as usual, about anything that transpired during his tenure as Vice President.

“Shame isn’t for writers. You have to be shameless,” says Roth, described by Jonathan Franzen (“The Corrections”) as “a person who really has decided he doesn’t care what the world thinks of him.”

Both documentaries are enlightening, at least in exposing the views of the featured personality — in Roth’s doc, sounding very much like his exit interview, for the day the author of “Goodbye, Columbus” and “Portnoy’s Complaint” passes from the mortal coil. Moreover, even without follow-ups from Cutler, Cheney’s statements should provide plenty of fodder to his detractors, with the New York Times’ Maureen Dowd using the film to tee off on the guy she liked to call Vice, saying Cheney “certainly gives certainty a black eye.”

Still, I found myself wanting the interviewers to exhibit at least some interest in eliciting more from the subjects — either asking them to elaborate on certain points, or defend their position in regard to others. Besides, Cheney’s a tough guy who has no problem being combative, and Roth has had decades to contemplate the reaction to his writing. Why not press them to address their critics?

Admittedly, there is inherent value in hearing from such figures at such length, and plenty of time to sort out dissenting views and analysis. Even so, in both cases the filmmakers feel like they missed an opportunity — dealing with the guy forever linked with weapons of mass destruction, and another well versed in mass distraction.

Philip Roth: Unmasked

(Documentary; PBS, Fri. March 29, 9 p.m.)

Produced by Cineteve and American Masters for Thirteen. Executive producer, Susan Lacy; producers, Fabienne Servan Schreiber, Lucie Pastor; writer-directors, William Karel, Livia Manera; editor, Stephanie Mahet. 90 MIN.

The World According to Dick Cheney

(Documentary; Showtime, Fri. March 15, 9 p.m.)

Executive producer, R.J. Cutler; directors, Cutler, Greg Finton; writer-producers, Cutler, Francis Gasparini.