Sunroom roof pulled out

Hi there. We have a 4 season room or sunroom that is attached to the back of our home. Recently we have noticed that the metal roof has pulled whatever attached it to the walls, out. The roof heats up and bows making about 1/4 of daylight visible from the inside middle of the ceiling. I have been told by a contractor that this is a common occurrence here in Florida because of the heat. Any suggestions of inexpensive ways of fastening it back down? We are currently looking into using a rubberized roof coating on it for decreased rain sound and increased efficiency. Any help would be greatly appreciated as we are a limited budget. Thank you