What is carpet roll crush?
As an Certified Carpet Inspector roll crush is one of the most frequent issues I am asked to go out and correct. It is noticeable immediately after or during installation. if it does not disappear in the first 2 weeks it can be professionally addressed. 98% of the time it can be fixed by steaming and pile lifting the carpet pile. It can happen to broadloom carpets or carpet tiles. If you notice roll crush talk to the person who sold you the carpet soon after installation. 
According to The Carpet &Rug Institute:
“Roll crush usually appears across the width of the carpet as areas of the pile yarn that have flattened due to the weight of the roll. Areas of crush may appear darker or lighter and usually are identified as widthwise bands. Roll crush is not considered a manufacturing defect. Most roll crush occurs as a result of stacking a large number of rolls on top of one another. Roll crush also may occur during shipping where rolls are loaded several rolls high.
Roll crush sometimes can be alleviated in carpet using steam or hot water extraction cleaning. Often it can be removed using a spray bottle and misting the area with water. Let it stand for five minutes and agitate with rug rake or by vacuuming. Most rolls of carpet will exhibit some degree of roll crush immediately after the roll has been unwrapped. In most cases, minor roll crush will disappear after the yarn has been allowed sufficient time to recover.”
Any carpet or rug new or old can experience roll crush if stored for excessive periods of time in an unconditioned space under pressure from things that are stacked on top of it. This can not be confused with water marking, shading or pile reversal that are topics of other ECO Blogs to come.