It was the fact that she wouldn't date Roger that kept Roger interested over the years. It didn't hurt that she was gorgeous and intelligent to boot. What wasn't there to like about smart, beautiful women?
While Roger wasn't a Gryffindor, he did share in the stubborn trait that they seemed to possess. At least, when it came to Cho.
"I sometimes do see them again or give them a call, but it isn't as if most of them are interested in settling down with a Quidditch player either." A lot of them were after the bragging rights that came with being with Roger. "They get to say that they went out with me and I get to enjoy an evening with them. It seems fair to me."