A few parchment rolls were made, but papyrus was definitely preferred for all forms of book, until the codex took over from the roll. Papyrus sheets could also be used to make a codex, but the result was unsatisfactory. Consequently codices used parchment as a rule, although papyrus codices from Egypt do exist. The gradual disappearance of the papyrus plant from Egypt meant that parchment was used almost exclusively from the 6th century onwards, until the technology to make paper became known, in the 14th century. Very late manuscripts are written on paper, and can be very hard to tell from early printed works.
Parchment looks like high-quality, thick white paper.
It has a slight tendency to curl, so the pages in a medieval manuscript tend to have a 'wave' in them. Quarto Standard size for a manuscript or early edition. Larger than A4, smaller than A3. In a codex, this means the first side of a leaf. Manuscripts do not tend to have page numbers in the modern fashion.