Rodaway himself admits that he is not the final opinion on the matter, but the evidence he presents in his book bolsters his argument on Culhwch ac Olwen's dating; the 1100 date favored by Bromwich, et al., was always based on flimsy evidence, anyway. As far as we can tell, the character of Peredur m. Efrawc did not exist prior to Chretien de Troyes writing Perceval, so there can hardly have been a pre-Chretien Peredur tale; the fact that the character's name was drawn from a Welsh translation of Geoffrey of Monmouth, the earliest MSS of which dates to the mid-13th century century, further supports the argument that Peredur is post-Chretien. Regarding your question about courtly material, I don't really understand your point - obviously a Welsh author familiar with French culture could have incorporated elements from it into a native tale - but that doesn't seem to be the case here, as there is no evidence for a pre-Norman Peredur tale. What we have here is a Welsh author reacting to French Perceval romances and adding in some traditional Welsh motifs to make the story more palatable to a Welsh audience.