I would say that I'm neither fat or skinny. I'm under the "normal" category in BMI, but I have slight tummy fat. Not like a big tummy, but definitely not those flat tummy you see on models. Is that a turn off?
No, a little roll (not a lot of rolls) or some overall softness is just fine on a woman. Being overweight is not. Unless a girl works out a lot, most girls are going to have softer stomachs. Be a healthy weight and I don't mind if your tummy isn't a rock hard table of abs. If you're normal for your height, don't sweat it. I'd be just fine with your stomach.
For most guys, that's no big deal. Most guys in your age group are mature enough that they don't expect girls to have photoshop-perfect bodies, and in most cases they have their own flaws and are well aware of them too. Anyway, for most guys, this is WAY down the list of things they care about. Personality, attitude, and compatibility are far more important, and far more likely to be a deal breaker than a bit of tummy.