I 'preach' the Fix-The-Source 'thing' all the time. I don't know why I didn't 'go into that' this time.
Carol - Steve is right. For now, you can clean the roof but if you're a masochist, don't fix the cause of the problem. (I don't believe you are.) A professional Tree Service can do the trimming job, or if you and/or your significant 'other' are handy, you can buy a few 'tools' and do the trim-job yourselves.
My best to ya and hope this helps.
PS: Here's a sample of my 'speech' when it comes to fixing the 'cause'. This post was made today (as was my Follow-up.) Termites and Ants In The House ...