It would be helpful to know who you are writing to as how and what you say will vary depending to your audience. Assuming you are writing to someone who is not a part of the company you are thinking of joining I would write; "I guess you've not yet been able to talk to the person who would be in charge of me (I assume you mean in your prospective job). If the job is stable, the company is serious, and the salary and conditions are attractive, I would be very interested in this opportunity. I trust your opinion and would welcome your advice on this and would ask you to indicate (not sure what you mean after this). I would also like to know what roles I would be asked to perform (not sure what you mean after this). If you can clarify what you mean by the two bits I don't understand, I will amend this further. Could you also indicate how well you know the person you are writing to as it is important to get the right level of formality.