That particular roof is Aluminum, even with the foam insert it is still not the strongest material. It can be walked on easily, the problem is trades lie about knowing how to and they smash it up. I flashed around a new roof mounted AC on the last one i did, the AC guy, (260lbs btw) is up there wearing heavy boots smahing all my new panels i just put in. Its not comp, you need to take some care and use common sense. If you smash the first panel you stand on then you should probably get off the roof. You will get not get a different result on the next panel you stand on.
The cost of this particular roof is high, the OP could very well get a SS for around the same $ and it would be far more walkable. The CM is great looking and its a good system, but i wouldnt put it on my home...id put that $ into SS or even a stone coated shake direct to deck application.