Make him a jolly man type, the kind who finds everything about the world wonderful and is just glad to be a part of it. Kind of like the big goof ball from The lone gunmen series. I wouldn't make him stupid like that guy was though. He could be the kind of guy that is always in bad situations but somehow, by sheer luck, survives (kind of like a Forrest Gump type character).
You could also make him a split personality. When he is out in the desert, where the




is hitting the fan, his "alter ego" takes over, making him the fast thinking, survivor type. But his normal self is simply jovial, kind of niave, without a care in the world. If the DM is cool, you could even have two character sheets with different skills.
Also, I would like to say just because the guy is a quiet brooding type, doesn't mean he wouldn't have lots of opportunities to roleplay. Look at Raistlin, would you say that he was not a strong "roleplaying" character? It doesnt really make sense for someone to be happy-go-lucky in the type of world you describe. I would think that the quiet brooding type, the survivor, trying to get past his distrust of others in order to survive and thrive in the world, would provide plenty of roleplaying opportunites.
It seems that without magic, and in a world like the one you have described, a fighting character would be in order. Perhaps someone based on the Aiel or desert people of the Anarach (can't think of their names).
TLG