Excluding sesame oil, the only Asian cooking sauce stocked in my pantry is soy sauce. In Asia, most vegetables stir-fries call for oyster sauce but without that, I have to create some kind of "sauce" base when making vegetables stir-fries (e.g. Sweet and Sour Tofu Stir-Fry) and tomatoes come into the picture.
Tomatoes not only sweeten up the entire dish naturally, the combination of tomatoes and soy sauce just means more flavor (more umami) for the dish.
The trick to a quick Asian stir-fry of a combo of vegetables is to cook each or some of the vegetables" separately' then combine them in a quick stir-fry towards the end of cooking. If you were to add the vegetables - in the sequence of which vegetables cooks slower (added first), to those that cooks fastest (added last), the heat of the pan is often brought down when you add in something raw, thus slowing down the cooking process.