Travel to the Engadin via well-developed roads via Julier-Pass, Albula Pass (only in summer), Bernina- and Maloja-Pass or via the Lower Engadine.
Zurich - Pontresina: 200 km, 3 hours
Milano - Pontresina: 175 km, 3 hours
Munich - Pontresina: 300 km, 4 hours
Basel - Pontresina: 250 km, 4 hours
When the snow is blowing, crossing the passes is only permitted with chains or 4x4 vehicles.
Look at that Road Conditions Map of the passports.