Considering he wasn't looking at her, the eye roll would definitely go unnoticed. And even if he had noticed it, Harry wouldn't have said anything about it. He didn't want to argue, didn't want to say anything that was going to start a fight... despite what she may think, he wanted this to go smoothly. In the sense that he didn't want to talk about the things that made him uncomfortable, thought he doubted that he would be that lucky. Ginny was full of things to say that would make him uncomfortable, he was sure.
When asked why he was here, Harry glanced over at her again and took the time to study the expression on her face before turning his attention forward as they headed down the steps to the first floor, and then headed towards the entrance so they could head outside and into the cool fall air. "I'm here because the Minister thought it would be a good idea to drag me here. He thinks the people could use a little Harry Potter in their lives. So here I am. He's going to "save" me." That caused green eyes to roll, and the cynical tone of his voice would give away just how strongly he felt about that particular subject. About the Minister in general, really.