Rice flour: weight to volume

Because of the different shapes, different pastas will occupy different volumes of space both before and after cooking.

There are two answers that readily occur to me, one simple one more complex.

The simple solution, of course, is just to make too much. Cook your pasta, put in the casseroles with sauce or adding the sauce after, depending on your recipe, and if you have too much (you should, you planned for it) let it cool, add mayo, mustard, onion, some pickle relish and make pasta salad. Or throw in soup. Or ....

Option two is to measure your pasta by volume when dry, assuming that it approximately doubles in size. So you'll need to fill one of your casseroles with dry pasta, and that should give you enough to make two casseroles worth, once you have cooked the pasta.

The weight of flour varies immensely depending on how densely it's packed and the humidity. If you've started with a weight-based recipe, I'd try to find a scale.

If that's absolutely not an option, I tend to approximate 100g = 1 cup.

Be warned, I've found some recipes that are really sensitive to the amount of flour and the difference between a lightly sifted cup and a scooped cup can really throw off the results. You might do better to try to divide another kg package of flour evenly and use the approximation that 0.6 lb is about 0.25 kg (i.e. one quarter of the bag).