My ratatouille is just my pasta sauce only with added chunkier vegetables such as green/red peppers,onion,whole cherry tomatoes and courgette....if available. I give the veg a blast in the frying pan till they are well charred before adding them to the sauce.
I also brown some chicken pieces, add them and that's it....all ready to serve. No idea if that's what a ratatouille really is or not but it tastes pretty good.