Since the satellites are more than 20,000 miles away, the change in elevation angle between the ground and the roof is infinitesimal.
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, certainly
Consider a triangle with one side being from the ground to the roof and the other sides from those points to the satellite. There will be a different angle, but the difference will be very small, hence I said infinitesimal (<<<<1 degree). For all practical purposes, it is the same angle, of course.