Early Christian Rolls

Until the third century CE, in Egypt and throughout the (primarily Mediterranean) area of Greek language and culture, the standard format of book was the roll, used horizontally. Only during the third to fourth centuries do we see the diffusion of the codex format: the direct documentation from this period on consists of an increasing number of fragments of codices compared to roll fragments. Hence, the most ancient codices have been subject to in-depth studies and the change of medium represents an epoch-making event. Two concrete pieces of data emerge from the general picture. 1. From the direct documentation, coming both from excavations and purchases, it appears that rolls were used for literary texts until the fourth century, and only on very rare occasions in the following centuries (there are some significant exceptions, which I will mention shortly). 2. Christianity spread in this period, and it is seen that Christians adopted the codex for texts of the holy scriptures. But what link is there between Christians and the roll format?