At a certain point you run into physical realities of living, growing things. You can use ratios to make homogenized items (mashed potatoes or sauces or caramelized onions or sausage). But even if you had two chicken breasts of the same mass they'll need different amounts of sauce or coating since they'll have different surface areas, and different cook times since they'll have different volumes.
I think any recipe for roasted vegetables has to be by volume of the chop/dice fwiw. There's lots of ways to chop carrots into 20g chunks, but they won't all cook well or evenly, so a 1/4" dice is what you'd call for (even if you call for 600g of carrots)
