Final answer:
Roofers roll out an underlayment on top of the plywood to protect the home from weather damage, which serves as a crucial water-resistant barrier beneath other roofing materials.
Step-by-step explanation:
Roofers roll out an underlayment on top of the plywood to protect it from the weather. An underlayment is a water-resistant or waterproof barrier material that is installed directly onto your roof deck. It is applied under all other roofing materials as an added layer of protection from severe weather such as rain, wind, and snow. The primary purpose of underlayment is to prevent water intrusion that can lead to mold, rot, and other structural damage to the home. It also provides an additional barrier against heat and sound. While insulation is used to maintain a climate-controlled environment within the home, shingles are the outermost layer of the roof system, and flashing is used to protect critical areas of the roof where water might penetrate, such as around vents, chimneys, and valleys.