Exercise: Attack on a Two-Round DES Cipher
Your Formulas are alright, but there is some additional information from the exercise/setup:

The exercise states, that $F$ should be considered as a blackbox (otherwise you could use the internal stages of $F$, as poncho already suggested). However, as I understand it you can stil evaluate $F$ on any input of your choice.

At this point, you can do a couple of things. First, you're already done without knowing it. As a hint: Read the goal of the exercise and compare the complexity with a brute force on your formulas. You only need 1 ciphertext/plaintext pair.

A more complex idea: If you have a lot of ciphertext/plaintext pairs, and you just want to distinguish the permutation from a random oracle, then you can do the following: Look for two plaintexts, where $R_0$ (32 bit) is equal. What happens then to the output? And what would happen in a truly random permutation? This is a distinguishing criteria.