Yes, Rowan County, North Carolina is where James ALEXANDER m. Margaret IRELAND. That marriage took place in 1773 before Iredell County was formed from Rowan County. In Iredell County there were Alexanders and Irelands who were neighbors - and there was a James ALEXANDER (b. ca 1760ish) who m. Elizabeth IRELAND.
I really don't know anything about these families other than that. The information that I have on James & Margaret who settled in Wayne County, Indiana is also from Norman - so I can't add to your information.
If this were my line, I would go back to St. Genevieve and St. Francois Counties and look at every ALEXANDER family who lived there between 1820 and 1830. I would begin with the census for those two decades. Then I would look at probate and land records.
In all likelihood, Rachel's family and her husband's family lived in the same neighborhood. So any region where you find both families would be especially important.
St Francois County was formed in 1821 from St. Genevieve County, but it's possible that your families lived on the border of these two counties and so you could find important information in both counties.
Rachel was a very common name - my early Alexander lines all had Rachels in them. So at this point I wouldn't count on Norman's line being the same as yours unless you can demonstrate that some of his line actually went to SE Missouri.