My rosacea wasn't diagnosed until my mid 40's and even now I'm not absolutely sure that's what it is - I don't have most of the classic symptoms and no apparent triggers.
I'm a mongrel, too - mostly Scots Irish but a lot of other bits, too.
I agree about washing the scalp more often. If I go more than 4 days, I usually really start having problems. I have to cleanse and scrub it well, whether by low-pooing or co-washing pretty regularly to keep it in check. I do best to go 3 days usually. I used to think going longer was giving it a break from shampoos, styling, etc., especially when I still used sulfates, but I finally learned differently.