How to tell if roof can handle solar panels?

[solar pete]

Hi Foo

You just dont attach panels using wood (you use the wood to create a structure to mount the panel rails), well we dont anyway. Those little 100watt panels are not that heavy, so if you can walk around on your roof no worries you should be fine. If you cant walk and or jump around on your roof then you probably have issues.

[foo]

I have a roofer that will install 10 x 100 watt panels onto my roof for an off-grid/battery application.
How do I know if the roof can handle the panels?
The roofer mentioned using two beams of pressure treated wood attached to the roof so that the panels will be mounted to those beams.
Does that strengthen the roof structure enough, is that amount of panels not that heavy, should I ask more questions?

Thanks for any information.