usually how much aromatics would you add for this recipe? half a shallot? 1 clove of garlic?

Also, if using ground nutmeg, how much should i use - about half a teaspoon?

Mother sauces allow you to personalize the flavor by adding an array of ingredients. It is really up to you and how strong of a flavor you want to add. For this amount of sauce, your suggestions of the shallot and garlic sound reasonable to start with. For the nutmeg, add a bit, taste it and adjust to your liking. Make sure to review the lesson on Bechamel if you haven't already done so. Cheers!

I have a midterm coming up this week that requires us to make a béchamel sauce.. Our recipe for culinary school says to add the cool roux to the warm milk.. Are there any advantages or disadvantages with this method?

The only advantage is that a cool roux's butter won't melt too quickly, so if not properly whisked right from the beginning the butter in a warm roux can melt out and result in a greasy bechamel. Just remember to stir or whisk continuously when combining the two. But I've never had problems adding a roux and milk together, no matter what the temperature.

Thanks so much! I have a fear that I am going to split the sauce..even though I don't usually have this problem..oh nerves lol

I discovered something called Sauce Flour recently. It is really great because it allows you to add more flour to a warm mixture if the sauce gets too thin. Simply whisk it in with manual balloon whisk in a Bechamel or stir in if there are other ingredients already there. Any small lumps disappear with cooking.
I have found that this works well with casseroles and meat based sauces if you add a bit too much stock etc.,and want to thicken it up again.
Any comments?

My first comment is that I had to look up Sauce Flour as I had never heard of it. My only other comment would be, If it works for you then that's what matters. As I cannot say whether or not it will give a sauce the same richness or flavor, as I believe there is no need for butter or fat with the "sauce flour", therefore; I can't really add much more than that without testing it out. Cheers!

Sounds kind of like a white wash? I think my only fear would be that it might produce a raw flour taste?

This flour is widely available in the UK and may be used instead of ordinary flour, with butter and/or fat and well cooked in the same way. However it really comes into its own if you want to thicken already warm or hot ingredients without risking lumps, unlike plain flour. Sorry, don't understand the comment about white wash. In my part of the world white wash is a paint!

When would you use a bechamel sauce? You can tell I'm a newbie. Thank you.

Not sure if you have watched the lesson on "How to Make Bechamel" but you may want to watch the Introduction topic of the lesson as we do talk about it's uses there.

You may also want to watch the lesson on "How to Make Roux-Based Soups" as we talk quite a bit about bechamel sauce in there as well. Cheers!