Can I freeze ricotta cheese ravioli filling?

yes, absolutely. You could use it up faster by using it to make lasagna or manicotti.
You could also add various things to it to make different variations. Things that would work as additions, imo are:
sundroed tomatoes, chopped walnuts, bacon, ham , italian sausage, prosciutto or chicken; chopped and sauteed fennel or artichoke hearts, spinach, mushrooms, pesto.
Endless options! You could also toss the mixture with very hot just cooked pasta (and any of those additions ) plus a little of the pasta cooking water (the heat would cook the raw egg in the mixture.) And i'm guessing you already know that you could fill more ravioli and then freeze them, to be boiled frozen in the future. And if, like sometimes happens when i make a big batch of canneloni and I have more filling than pasta sheets, you can use wonton wrappers to make more ravioli. They are found in the produce section of most regular groery stores in my area.