For roll paper buy local. Shipping will kill you due to the obtuse size.
Look for large theatrical supply houses, not camera stores. They typically have a much better supply of roll paper that all but the absolutely largest camera stores (B&H, Adorama, Calumet, etc).
In Colorado you may be limited to Denver, but there might also be something in Boulder, Colorado Springs, or Ft Collins.
You are definately not going to find roll paper in Red Feather Lakes or Walden.
The common 9 foot roll paper comes two ways, with a center spindle, or without (like toilet paper). The spindle adds about 5 to 10 dollars to the price, but makes the roll much easier to deal with when the paper roll starts to get toward the end. New, with or without a spindle is about the same, but as the paper is discarded, the center spindle gives the roll a lot more robustness
Enjoy! Lon