This article doesn't cite everything that Roko says but seems like an ok citation for the general idea of using nukes to cover the poles with dust. I don't know how much of a reliable source that is. I am under the impression that Zubrin in his book the Case for Mars suggests various methods for covering the poles with dust but doesn't discuss using nukes. Given Zubrin's general approach and the extensive nature of the book, this would suggest to me that Zubrin doesn't take the idea seriously (and he's clearly thought about Mars colonization more than anyone almost else). However, the book is old enough at this point that if this is a new idea he may just not have been aware of it at that time.