If you have the first role already filled, you don't really need me any more. I would have liked to know when you wanted the samples, as well as a little guidance with the mood and atmosphere during reading, but you've found one without any consideration for any of the other eligible actors that you called on. You really should have specified that there was a deadline. First come, first serve roles rule out the possibility of any better talent showing up and is overall very unprofessional, but then again, so is not specifying when you want the samples in.
I may sound rather affront and harsh, but I feel insulted. I was going to work on it, but what use is it now that you've already brought someone on for that role? If you were still taking auditions for it, but had said person in mind, it wouldn't cheat the rest of the people you've asked about for said same role. If I didn't make the cut, it would be a fair defeat and I'd not be as irritated as I am.
Believe me, I want to do this. But right now, there's no point.