Adam, based upon your picture it is hard to determine the severity of your roof cracks. Some small holes also appear to be present. My experience has been to use fiber glass with resin. For cracks drill small holes at each end of the crack and carve out the crack creating a vee to apply the fiber glass . Fiber glass comes in different applications such sheets, rope and cat hair which seem to fit your use. Sanding and repainting of course are also required . Best of luck
