Preheat oven to 220C or 200C fan forced.
Line a baking tray with baking paper and place pumpkin on prepared tray and lightly spray with oil and then bake for 20 minutes and then add tomatoes and bake for a further 10 minutes or until pumpkin is lightly browned and tomatoes softened.
Meanwhile cook the pasta in a medium saucepan of boiling salted water, following packet instructions, or until just tender and then drain.
Heat oil in a non stick frying pan over medium-high heat and add the chicken and cook stirring for 5 minutes or until lightly browned and then transfer to a plate.
Add onion and garlic and cook, stirring for 5 minutes or until softened and then return chicken to the pan.
Blend cornflour and a little evaporated milk in a jug and stir in remaining milk and then add this milk mixture to the pan and bring to the boil, reduce heat to low and simmer stirring occasionally for 3 minutes or until sauce thickens slightly.
Add the cooked pasta, olives and roasted pumpkin and tomatoes to the sauce and toss gently to combine and serve pasta sprinkled with cheese.