I've picked up tons of rolls of vinyl, laminate, canvas, banner material, etc from shops that close down... a lot of it rolls that are highly unusable unless i have a 102" machine or something equally as unwieldy ... I just make sure the area I'm going to cut is done with a hand saw (have a really nice japanese saw that cuts extremely clean) and the edge area is taped with about 3 or 4 passes of painters tape so it won't tear the edge wide open when I hit the bottom. you can do the same thing with a mitre saw if the roll is small enough ... used to do it with a pull saw.
Doesn't work with canvas though ... still don't know how to cut that one down properly ... everything causes the edge to unravel.