Suppose I have medium-sized roma or plum tomatoes and want to make a jar of pasta sauce. Assuming I do not add mushrooms, peppers, onions or a significant amount of other fillers, roughly how many tomatoes will make 1 jar of pasta sauce?
Tomato size varies, so number of tomatoes is going to be so rough as to not be globally useful. Weight is pretty good, though.
The NCHFP's tomato sauce page says you need an average of 6.5 pounds per quart of sauce, so for 24 fluid ounces you'd need 4.875 pounds (4 pounds 14 ounces, or 2.2 kg).
I've found nutrition data saying 62g for a plum tomato, and Wikipedia says 57g (2 oz) for a roma tomato, so that'd be 35 to 39 tomatoes. But the roma tomatoes I often see in US grocery stores could easily be twice that size, so with those you might need more like 15 to 20.
Of course, how much you cook it down has a huge effect too, but without trying a specific recipe, it's pretty much impossible to know where you are on that scale.