If you're in an ICE car with an automatic transmission the car tries to slowly roll forward. If you're in a manual transmission ICE car you have to press the clutch or pull the car out of gear and then it rolls forward or backward unless you're on flat ground.
I'm just curious about what the Roadster does when drive is selected and you're stopped. My guess is that it will sit still and you won't have to hold the brake as it would be a waste of battery power to mimic an automatic transmission and have the car slowly roll forward. If the car does indeed sit still on flat ground while stopped, what happens if you stop going up a hill? Will the motor allow the car roll backwards?