what treatment can i give to my roses they have black spots appear on their leaves

This is a question that gets asked regularly, if you go right to the very bottom of the page onto the black piece, click on PLANTS then scroll down that page until you come to roses, click on the underlined word roses and you will get the page with all the questions and answers relating to your question.

You can buy a spray for this but also remove all affected leaves and burn them or dispose of them some other way. Don't compost them.