They do not have to be fed vertebrates even though that is what they are adapted to eat in the wild (up to 90% of the prey items consumed by volume are vertebrates).
As they get larger you will need to feed them bigger food items.
The higher the quality food item when fed to the frog while growing the larger the frog will grow if it is a female (males tend to be smaller).
If they are taken care of small ones are hardy (but I prefer to start them on fish when they are little).
If you go with invertebrates you will have to supplement the food items with a vitamin/mineral supplement. (which should also be used when feeding rodents)
Ed