I bought that exact laser thermometer on black Friday. The main exterior wall in our bedroom is facing South. I'll shoot all the ceilings. When I get home
I've had one of those laser things for about 20 years. The first one I bought cost over 200 and was worth it's weight in gold for finding leaks and temp problems. I use it on the diesels in my boat every time I run it just to see if something is hotter than it should be. Saved me thousands over the years, but for this there's no better tool.
If your ceiling is hotter in one room than the other with foamed attic, then you probably have a duct problem. Restriction somewhere I bet.