Are persimmon leaves a good mulch to use in a rose garden in winter?

Generally speaking, leaves are not a good mulch for anything until they have been composted. Roses are susceptible to fungal diseases, the spores of which over-winter in the leaf litter around the base of the plant. If you live in an area warm enough to grow persimmon trees, you don't need to protect the rose crowns from freezing, so all you need to do is top-dress with a good compost. To compost your persimmon leaves, which are large, try chopping them up and mixing them with grass clippings to get the composting process started quickly. Properly prepared compost needs to reach at least 180 degrees to kill all pathogens, but if you can't achieve that, at least let the compost rot for a year or so, and turn it to get oxygen to the middle of the pile a few times during the year.