My baby is 2.5 months. How to train him to roll over? Any game or play?

I agree a little to soon unless he is ready already by himself my first was rolling over immediately after birth and was very advanced in general for movement for a newborn but if and or when ready a ball is also a great interactive to help with that my second loved to watch the ball roll towards and away from her. But make sure he has good muscle support and is able to hold his head up very well first and tummy time is always the best for getting them to roll over. Don't feel like just because friend/family or even doctors charts for development of other babies means its time for your little one too. Every baby is different and goes at their own pace, some more similar then others. But you know your baby best!! also they gave great floor mat toys for tummy time to look at if your little one is more apt to music like my second was things with like a feet piano is a great one and will also encourage the process of rolling over. Good Luck!!