While the sweet potatoes are cooling, combine the ricotta cheese, parmesan cheese, and salt and mix to combine.
Remove the skins from the sweet potatoes and add the sweet potato flesh to the bowl of cheese. Using a hand mixer or a potato masher, mix until very smooth and combined.
Add the flour to the sweet potato mixture and, using your hands, combine the flour with the sweet potatoes. Continue adding the flour, kneading the dough after each addition, until combine. Be careful not to over-mix the gnocchi dough. Once the dough is fairly smooth and easy to handle, transfer it to a floured surface.