I want to preface this by restating that while South American flags are generally pretty bad, their designers do try. Asia – I’m looking at you – you’re a continent of cop-out flags with few subnational designs.
Anyhow, back to this one. The blue is for the air, the white is for peace (both of these first two are hackneyed.) The green is for forests and fields. That’s been done. The star represents the fact that Roraima is a Brazilian state, among all the others. And finally, a bit of more rare symbolism – the red line represents the equator, which runs through the state. Most of the state lies north of the equator, hence the red line is about 2/3 of the way down this flag.
The diagonal bands of color are pretty distracting; horizontal would have been much better, especially because the blue band represents the air, and the horizon in Roraima is just as horizontal as most places. And while the placement of the red line makes sense geographically, setting the star on it has a Mario Brothers feel to it; like if you jump from under this flag and hit it with your head, you get an extra life.