Detached garage - insulating ceiling or roof?

We have a detached garage that no insulation, except for insulated garage doors that face West. No insulation inside the walls, ceiling, or in the roof.
Would it be a waste of money to to spray foam in the attic roof or have insulation laid in the attic on the sheetrock ceiling? I believe the soffit does have vents.

I have a portable AC unit I use in the garage to cool me off when I'm out there piddling but wondered if insulation the attic would help the garage stay cooler even though the walls are not insulated. Thanks.