I know this sounds a tad strange, but i need to know..?!

If he's not in pain, then chances are he is fine. Is he in pain?

If he is in pain then he needs to correct it. If he is erect, have him squeeze his head (the penis head) with his finger and thumb, this will help to "deflate" him and he should be able to roll the skin back up. If it is stuck behind the head and you can't get him flaccid again to move the skin back, get him to the Dr right away. Although rare, it can actually cut off the circulation to the penis and that is serious.
I don't mean to alarm you (or him) but it can turn serious quickly if you don't know what can happen. Most of the time squeezing the head and apply some ice to the shaft (not the head) will make it go down enough that you can get the skin back up.
I hope this helps.

lolz happened to me once.....well I got 2 things to tell u!!

1. take a pizz because it might be full
2. horny!!! AHHHHHhHHHH ur dreaming of some1

those 2 things and u rolling it down caused it and u need to fix 1 of them

Rolls down?
Does not come back up?

I don't get it.