Squeeze the grated cassava using a kitchen cloth or cheesecloth (like the one used for preparing homemade pap) to remove as much liquid as possible. The cassava should be very dry with little liquid.
Mash the bananas well using a fork, masher, or food processor.
Add the cassava and salt to the mashed banana in a medium sized bowl, and mix them together very well. The mixture should be firm enough that it can be rolled into balls.
Use your palms to roll about 2 tablespoons of the mixture into bite-size balls.
Heat the vegetable oil to 375 °F in a deep skillet or a saucepan. You can check the oil temperature by dropping in a 1-inch square of bread—it should take about 1 minute to brown.
Place the cassava balls gently into the hot oil and fry until golden brown. Do not overcrowd the pan—work in batches as necessary.
Remove the fritters from the hot oil, drain, and serve fresh.