What is the role of male nipples? Are they a part of spots of arousal?

Well I don't really no but I no when I mess with my mans it does nothing it does not bother him one bit so I don't think so

They arouse me if you rub them right. Probably a preference thing for guys. My wife reaches around and starts to play with mine, and next thing you know were taking our clothes off :)

Males have nipples because nipples form before the sex is determined in utero. I heard about that from Dr. Edell. My husband says that they are not a "zone" for him.

In some societies males breast feed. It was even documented as far back as 1859. Milkmen: Fathers who Breastfeed

Some men have sensitive nipples and are aroused by nipple play and some - it just does not do a thing for them.

You want to read more about why men have nipples - Evolution 101: Why Do Men Have Nipples?