Often, power lines can cause RF interference with a TV signal. Probably best to move it away from there - and if you include the danger of contact with the power lines, a new mounting bracket is no big deal.
As you probably already know, height will be helpful for reception in the mountains; any neighbors to ask for local advice?
When you talk about drilling into your roof, are you just talking about a mounting bracket - or are you drilling through the roof to run wires???