I know the Model X has sunshades built in to that purpose. I'd assume Model 3 will come with similar/better features. It could be quite inconvenient otherwise, and quite a silly mistake on their part.

Having said this, many sunroofs are so dark you barely realize they are there. Not sure that is the case for Model 3, but both my last car and my current one are like that. I have a sunroof but it is quite dark and I never close up the shade on it because sun virtually never bothers me. I'd guess particularly sunny areas would require a sunroof, but not Rome, or anywhere I've ever gone with those cars.