Why is the plaster in your 1-year-old pool turning rough over the last few weeks?

This sounds like a water chemistry problem. If the surface was smooth prior to the last few weeks, then the water chemistry is out of adjustment. The problem could be related to high or low pH,total alkalinity or high or low calcium hardness. The roughness could be etching of the plaster surface due to corrosive water. It could also be scale depositing on the surface from high pH and calcium levels. Get a full water test on the pool water to find out the source of the problem.