The gallery is the product, and most roofing galleries cannot be used
A roof is a visual purchase, and the standard grid of unlabeled photographs answers none of the questions a buyer has.
Homeowners looking at roofing work want to know what a specific material looks like on a house like theirs, in a color they are considering, in a neighborhood they recognize. A wall of thumbnails with no information satisfies none of that.
What makes a gallery useful is the labeling. Covering type, product line, color, roughly where it is, and ideally what the house looked like before. That turns a decoration into a tool somebody uses while deciding.
Filtering by material and color is worth the effort if the volume justifies it, because that is exactly how a buyer narrows down. Failing that, grouping by covering type is most of the benefit.
The before image does more work than the after. A roof that was failing and is now fine tells a story. A photograph of a nice roof tells the reader nothing they can use.
Keep it current and keep it real. A gallery that has not changed in three years reads as a company that has not worked in three years, and stock roofing photography is recognizable to anybody who has looked at more than one contractor site.