Andy's take is positive and agreeable, albeit short and thus unable to look at the whole picture in detail Gurren Lagann deserves, but that's blogging for you.

But the most interesting character in that respect is Rossiu. He's there to comment that, no, you can't run a society off of balls and recklessness alone; at some point you need an accountant, someone with the patience and attention to detail to do the paperwork. But at the same time, the show uses him to illustrate the limitations of that kind of thinking. Rossiu is fundamentally risk-averse, and so that limits his thinking; he'll settle for a sure tragedy over a possible victory, every time. What's worse, though, is that he keeps trying to take charge; by his lights he's obligated to, because the idiots who keep winning battles keep almost losing them.

It's also typical for Gurren-Lagann to place Rossiu into a network for inter-related stories (e.g. Kinon's). It's viewer choice to focus at anything specific, for example if Kamina is a "blowhard", or how awesome Yomako-sensei is. That's how "surprising depth" is to be used for greater enjoyment.