I'd unroot just in case. However, in my experience, the people working as reps for those phone companies know extremely little about phones, and whatnot. I'm sure that the majority of them don't even know what rooting is, or what the superuser is. They'll know about jailbreaking, since it's so popular, but not rooting.
So ya, I'd expect you to be safe if you didn't unroot it, but if I were you, I'd unroot it anyways.