Here is a quick YouTube video I found that shows the forward roll as I described. I don't know the instructor, his dojo, or even his organization, but it is very similar to what we do in AAA aikido. It is important that the leading arm be unbendable as the person goes forward. A collapsing lead arm is the formula for a broken collar bone.
No, improper body alignment is the formula for a broken collar bone. If your body movement is correct, there is no need for a arm at all during the roll.