Preheat oven to 200˚C/180˚C fan-forced. Line a baking tray with baking paper.
Heat oil in a medium frying-pan over medium-high heat. Add mushrooms and thyme. Cook, stirring occasionally, for 4-5 minutes until mushrooms are just tender. Season. Set aside to cool slightly.
Meanwhile, using a small sharp knife, cut a small pocket into the top of each bread roll.
Combine cheese and green onions in a bowl. Fill each bread roll with the cooled mushroom mixture then top each with cheese mixture. Place rolls onto baking tray. Bake for 10 minutes or until cheese melts. Serve.