Here's why:
* "Myself" is a reflexive pronoun: It refers back to the subject of the sentence. You can only use "myself" when you've already mentioned yourself as the subject.
* "I" should be used instead: The correct way to start the sentence is "I and Robert are..."
Correct Examples:
* "I and Robert are going to the movies."
* "Robert and I are going to the movies."
* "Myself, along with Robert, are going to the movies." (This uses "myself" correctly, but it's a less common and slightly more formal construction.)
Remember, the order of "I" and "Robert" can be switched, depending on the emphasis you want to place.