It certainly can be on a mast; I put mine on a (short) steel tube mast, and it's been a great improvement on service that was already a vast improvement over Hughesnet-provided satellite.

He mounted the dish on his roof. There are still some tall trees in the way of the dish.

Here's his YouTube video of the installation:

https://www.youtube.com/watch?v=ynsCVOz7jv4

Mine is mounted near the top of my roof's ridge. The problem is there are 8 trees (five of them more than 75') around my one-story house.