The point that you want to control every thing is an illusion (in my humble opinion) you are always dependent on the tools you are using (otherwise you can write your own, but thats not the point)

Your real motivation(if i understand correctly) is to fulfill the requirements good enough for you to be satisfied as pass (and not do the absolute best that you could have done)

If you get into the whole notion of how every thing works exactly you wont be able to move forward. Like I know that there are aspects generated for Roo, how they are done, how aspects really work (with all the reflection stuff) I have very little idea, but hey, it works. I don't have to create getters ..bingo.

You can start with some of the most basic things first like the core spring and hibernate architecture. (Even there you just get to use things, its very superficial knowledge to know that this xml config does this and this annotation does that, but its still good to go). OSGi is a beast in it's self.

Later you can focus on your particular technologies. I would imagine it would be a good idea to learn the integrating technologies in isolation (like eh-cache, gae etc) and then lean how it works in roo. Otherwise you will have too many variables on your plate. Just a thought.