The 2nd picture on this page is interesting: https://electronics.stackexchange.com/questions/271674/tesla...
See https://www.quora.com/Why-don%E2%80%99t-Tesla-cars-need-a-ge...
Electric cars do not have a gearbox and just have one rotor. This does place them in a disadvantage when starting though as there acceleration is affected. Formula E cars, have started using a 3 gearbox for their cars in order to have a faster start.
So it is possible that the Roadster does have a gearbox.
Most high performance cars only shift once before 60, and with modern dual clutch transmissions it only costs a fraction of a second.
The only way Tesla are going to get below 2 seconds is either with non-street legal tyres (cheating!) or some new tyres that nobody else has.
The Roadster is significantly faster than other supercars from 0-60 on the same tires, so the advantage must come from much more efficient anti-wheel slipping from the three electric motors coupled to AWD. This dramatic speed advantage is probably a result of the ability to quickly alter the power output per wheel to minimize efficiency losses from breaking traction.
> it only costs a fraction of a second
In other words: exactly the scale of the differences we are talking about. In addition to the short interruption itself I guess that it also takes a few millis until traction control has settled after a shift.