W/O further damaging the roof, the roof line, or walls, you need to wait until the ice melts. Everything I read and know talks about PREVENTATIVE measures; NOT what to do if you have ice up on the roof now.
What you can do is wait until the day is at its warmest and gently chop at the ice to see if it comes up. (Be careful on that ladder!) The reason you want to be gentle is because if you aren't, you'll damage the roof and have a worst problem than when you started! Chopping too hard at the ice may break shingles, split the sheathing, or worst. So, the true test is ... If you can't remove any ice by HAND, don't remove it. Do you know why you have the problem? Is it because of a bad gutter installation? Is it because of an attic ventilation problem? We can certainly help you with what you can do to prevent this in the future.
My first suspicion is that the part of the roof DIRECTLY over the house is warmer than the part that hangs OUT beyond the house line. Hence, the snow melts on the warm roof, and freezes out over the edges. If your gutters are clogged, and downspouts too, with either debris or ice, that's something you can do now. Also, if you have trees or large bushes blocking sunlight that would otherwise shine on the roof, trim or remove them now. (The sun is an ally.) I wish I had better news for you. Since your post is kinda getting burried now, e-mail me directly if you have any more questions. I happen to 'stumble' on your follow-up.