I bought some cheap RA-4 (color) roll paper on eBay a while ago. I've cut it into sheets using an ordinary paper cutter. I measured out the size I wanted to cut and taped down some scrap paper at that exact distance. (It was actually beyond the width of my paper cutter, so I taped the paper onto a piece of scrap wood I had lying around, fitting the wood against the paper cutter.) I could then pull the paper from the spool, measure by feel, trim, and put the paper into the paper safe. IIRC, it took me about an hour to cut 100 sheets. It would have gone a little quicker if I'd rigged something to hold the roll of paper, but I didn't; I just lifted it and turned it by hand to pull out the paper, then set it down, measured, cut, and repeated.