I do have a lot of ice and snow on the roof should I install an ice melting cables
No. Best case scenario you just waste the money that it would take to install them, worst case scenario you create a problem that didn't exist before.

Ice dams are typically created by sharp surface temperature gradients on roofs, usually caused by inadequate insulation in the attic.  Heated air escapes through the attic and warms the roof deck, melting the bottom of the snow accumulated there.  The water runs down the surface of the roof until it gets to an area that isn't being heated from below (typically the eaves), where it freezes again and creates a dam.  

If you don't have an ice damming issue and start melting snow off of the eaves, the surface temperature gradient will be at the top of the ice melting cable.  Gravity will be on your side in this case, but there is still a risk that you'll get ice forming above the ice melting cable.

Finally, having snow accumulate on the roof is only a problem if there is too much weight. Outside of that, you want to have snow on your roof because it provides some additional insulating value and an excellent wind barrier. As an interesting side note, you can see this incorporated into traditional building designs in different parts of the world.  Areas with heavy snow falls tended to have steeper roofs, but they get less steep as the snow fall drops off largely in order to balance the amount of snow that stays on the roof.