#1 This year, on one of my rose bushes, the flowers are small with several branched out stems/blooms. Does this have anything to do with how I cut it back in the fall? I live in Michigan. #2 What is the cause of the rose leaves looking like this? Is it an insect or a disease? I have tried to attached pictures.
It could be that the rosebush in question was a grafted rosebush. The top part of the bush is the rose we desire and the bottom root system part is a totally different rosebush that is very hardy and thus is used for root stock. Sometimes the desired part of the rosebush dies over winter leaving just the root stock which can send up shoots of its own. These shoots turn into canes that typically do not looks anything like the rose we bought and wanted. Just from your description I think has happened to your rosebush. It is best to dig it out before it becomes unmanageable and plant a new rosebush there. It can be the same type of rose you had or something new you wanted to try. Here is a link to an article for you on this subject as well: https://www.gardeningknowhow.com/ornamental/flowers/roses/own-root-roses-grafted-roses.htm