How much do asphalt shingles cost?

According to Groome, for a single layer of asphalt shingles, with no need for repairs, the average cost for roof replacement would be $1.25 to $1.75 per square foot. "Anything more than that is way out of whack," he said. However, if there is bad wood or the need for a total tear-off the cost goes up by several dollars a square foot.