A roofer in a gray sweatshirt and orange hat walks on a unfinished roof at a lake-side home.
The roofer is putting on shingles.
Being on a roof does not automatically imply that a roofer is putting on shingles.
The roofer could be putting something else on, not necessarily shingles.
just because he is a roofer doesn't mean he was putting on shingles.