I love fish and courgettes, tomato etc. don't in an oven. I'm gonna be on holiday in a third world country where people do not have ovens in their home and just usually use a stove of some sort.
How do people in this countries get food cooked, like an oven, grill etc. or are my only options stove top frying and wet heat methods?
Maybe they don't. You can't replicate roasting on a stove top. With a grill pan, you can get in the ball park of grilling, but you would miss the major flavor contributor resulting from drippings hitting hot coals or grill burners.
Rather than trying to replicate something you do at home, I would suggest, that when on holiday, you embrace the culture of the place you are visiting. Leave your favorites from home behind, learn about the culture of the place you are going, participate, and learn something new. You can return to the methods you use when you come home.
This is wrong and a bit ignorant. Not all "third world countries" are alike.
Most countries have an "oven" of some form in their traditional kitchens: it's just not a branded appliance with an electric element, temperature setting, timer, or glass door.
If you're staying in guest accommodations, you won't have anything to cook with - exactly what you'd also expect in the West. I would recommend regardless that you take up some kind of cooking class to learn how to make the traditional food with the traditional ingredients in the traditional kitchen.
If you get an oven, you'll probably be dealing with a clay oven fueled by charcoal or wood. This is arguably the superior way to cook because the temperatures are far greater, the natural humidity, circulating air, and the excellent heat distribution and retention due to their shape. Alternately, should you be so lucky to try tagine cooking, you might discovery the sublime flavor of braising fish and vegetables in their own juices.
