If it has granules on it, try to scrape some off. Lay down a layer of mastic. Try to use the same material, place it in mastic and nail around the edge. Put a layer of mastic over the edge, and over the nail heads. If it is shake or wood shingle, you can wear golf shoes in an emergency, to walk on steep wood roofs without doing a lot of harm.
Dull spikes work the best, giving some grip without splitting the wood.
There are overshoes that are sold, which strap to your boots and do pretty much the same thing. As with any product at any height, care must be shown to assure your safety. Do not attempt steep roof repairs if you are unsure of your abilities. A long rope thrown over the roof and attached to something immobile. A tree, car, something that will not move.