That would be true if aerodynamic drag was the only factor, but there is also several others, like roll resistance, gradient resistance and so on. At higher speeds, a roof rack will play a bigger role, but if you go for a type like the one in the picture, a Yakima flushbar, its barely measurable at normal speeds.As a note of warning, anything that increases drag, like a roof rack, amplifies efficiency loss in an EV vs what would be seen in an ice car due to the inherent efficienticency.
Made up example. An EV that is 80% efficient, a 10% reduction by drag would see an 8% reduction in range where an ice car that’s 20% efficient would only see a 2% drop for the same drag. I think the actual number is close to a 5 fold difference on average between EV and ice.