Firstly, I am a cynical old so and so, so bear that in mind. I also keep my cars for the best part of a decade normally, so I buy really cautiously. If anything is not quite right, I walk.
From your initial posts, there are too many little niggling "Hmm, that's odd!" triggers for my liking. Maybe I'm wrong and it's all good, but I don't like unpleasant surprises when it comes to buying cars, and dents in the roof definitely come under that category.
As I said, it's a Spidey-sense thing, not an opinion based on fact. If you're a bit twitchy about the purchase and are considering a refund, it might be just cold feet at the prospect of handing over a lot of cash (I get that), but it might be your subconscious trying to get you to notice something.
As you tend to keep your cars for a long time too, I'd be twitchy about how good the repair to the roof is going to be. How's it going to look in 5 years? How long is the repair guaranteed for?
I am hyper-cautious and am probably at the extreme end of the scale when it comes to nervous buyers, so bear that in mind when reading my concerns.
Incidentally, my last car had a dent in the sill when I bought it. Never gave me a moment's trouble.
The rear door which had been repaired before I bought it started rusting after about 10 years, though. That was a nuisance.