I've had the same roommate for two years, and the one thing that we can never agree on is hair. (Actually, we don't understand each other on a lot of things, but that's beside the point...) For your frame of reference, she's an African American with big, curly hair and I'm an Asian American with straight, flat hair.
Back when we lived in the dorms, she'd always have this problem: instead of choosing clothes and then creating a hairstyle to match it, her clothes HAD to match her hair. Conversely, I would wear whatever I wanted with my usual clipped ponytail or straight hair. Though I couldn't tell, there were certain hairstyles that my roommate had to pick out certain clothes for in order to feel comfortable presenting herself. For instance, sometimes she felt she couldn't let her hair down for a certain outfit, unlike me.
It was really surprising for me to learn about the amount of hair care products she had. She had bottles and bottles of conditioner, oil and special shampoo to maintain her hair. Whenever she did her hair, she'd put a lot of the products and I'd see no difference. She's fast with her showers (10~15 minutes, tops). Whereas, for me, you'll see me in 20~30 minutes (an hour if I had a LONG day). The majority of time spent is simply rinsing out my hair. If you put oil, water, or anything liquid in my hair, it'll show it. If you do the same to her hair, it'll just absorb everything and look as big and poofy as ever. I'd be surprised every time she came out of the shower and it'd look exactly the same as when she went in. Even if there's a liter of water in it, her hair would still defy gravity (alright, maybe not a liter, but you get what I mean).
I have oily hair. (My roommate likes to joke that we should switch oil content--- she NEEDS oil.) I personally don't feel comfortable going out unless I have washed my hair. She thinks it looks fine, but I feel gross. I feel like my hair is too flat, and I wish I could have more volume (as I wistfully look at my roommate's hair). It's evidently obvious when we both put our hair up in buns. Hers hair gives her a whole 4-inch increase (no lie) on the top of her head, while mine slides down to the bottom of my neck, protesting it's very existence.
However, even though our hair is different from one another, we do agree on some things:
1. Braids are a pain. They look pretty, but for us, it's not going to happen. Mine magically untangles itself in a couple minutes (I'd be lucky if it lasts 15 minutes). In contrast, her hair has so many curls coming out of it that the sleek braid becomes a frizzy mess in a couple minutes too.
2. "I woke up like this" doesn't exist for us. (Okay, I'll speak for myself. It might exist for her, but definitely not me.) We need time with our hair...at least 5 minutes. Though tangles are a horror, toning the arms is great (for her more than me).
3. We like each other's hair a lot and sometimes wish for it. However, at the end of the day, we'll stick to our hair: the good, the bad, and the tangly.