Am I a cousin of Queen Elizabeth I?

The answer to your question is, I don't know. However, I was under the impression that Henry VII and Elizabeth of York were very much in love and that he never took a mistress (during his marriage of course). If that is the case and uming he never had any pre-marital relationships (which is highly doubtful coming to think of it) then this Sir Roland de Velville was not related to Henry VII and therefore neither are you.