Aluminum angle pieces are de rigueur for mounting panels. Most guys use two angle pieces in each location, one attached to panel and one attached to RV roof. This allows for easier removal and installation. The "Z bracket" is an alternative. Some of the better installations I've seen use aluminum struts and the modules are attached to the struts.
If attaching hardware into 3/8" plywood, it's a good idea to fasten through plywood into a roof truss, if possible. Toggle bolts also work but you'll have bigger holes and more work to use them. Inserts are another alternative.
FWIW, I have a bigger 235 module and a 4-way tilting mechanism on my aluminum roof. Besides the sealants, it is attached with 3 fasteners through 2 X "U" channel, each fastener through the roof and into a truss.
The examples of member installations that CA Traveller is kind enough to maintain a list of, pretty much cover the different types of installations.