Every morning and some evenings a squirrel runs across my roof.

there's obviously access to that roof, usually a tree branch. Check outside for that and trim it back. If it's INSIDE? I'd get a humane trap and start trapping.

The tree branches were cut. I believe it's travelling on utility line(s). It's scary. Where can I purchase a humane trap? Sorry I don't know about these things.

it is illegal to trap squirrels in many places in the United States. Call your County Animal Control. They would be the best ones to help you.

If you do not hear it inside the attic, it most likely travelling across the roof and has not gnawed a hole in your facia board. If you were to trap it, what would you do with it then?

There are usually more than one squirrel. And they keep coming back. What are you going to do then? I hate them and call them tree rats. I have an oak tree in my front yard and they nest there. Yes, their antics are cute - but still... I have learned to make peace with them and share my yard.

Good luck!

Hope Animal Control has an answer for you. Best to you.

If you can reach them, cover the openings with Vaseline, which will make the roof areas slippery. The squirrels shouldn't be able to run around then.