Place prepared vegetables on large baking sheet, drizzle with olive oil and scatter with rosemary and salt & pepper to season. Roast for 15-18 minutes or until just tender. Allow to cool. Increase oven temperature to 220°C/425°F/Gas Mark 7.
Take one pastry sheet and lay one on a lined baking sheet. Place the vegetables on the pastry in an even layer, leaving a border of approx. 1.25cm.
Fold the second pastry sheet in half down its length and using a sharp knife make cuts down the folded side, at 90° to the edge towards the opposite side, leaving a border of 1.25cm down that side and the short ends.
Brush base pastry border with beaten egg. Open out second pastry sheet and lay over base, press edges together, trim off with a sharp knife and knock up edges to seal well. Brush top with beaten egg and scatter over a little more rosemary. Bake for 20-25 minutes until risen and golden brown.