My skepticism has now received support in a recent publication by Nigel Morgan:
"The litany not only contradicts the destination claimed for the book, but also its date. ... In the litany ... there is an erasure of the fourth saint following the three English martyrs Alban, Oswald, and Edmund. There is little doubt that the erasure is of ... Thomas of Canterbury. The litany text ... must therefore be after 1173, and the connection of the book at the time of its making with Abbot Roger and Reading must inevitably be completely abandoned. ... neither Abbot Roger nor his institution was its original destinee"Nigel J. Morgan, English Monastic Litanies of the Saints after 1000, II: Pontefract–York, Henry Bradshaw Society, 120 (London, 2013), p.33.
The old image-link seems to be broken, but a large version of the image is available here.