I'm sure you've read baby books that say infants should roll over at four months. The range for rolling over is about three to six months, however, and chubby babies generally are on the later end of this range (more weight to move!). There is a range for all developmental skills, and just because a baby performs a particular skill early does not mean that they are any smarter, better, or more coordinated. Thus, I would say that if you want to put him on his stomach for a little while to give him a different view of the world, that's fine. Once he starts letting you know that he's unhappy, switch him to his back again. What you'll probably find is that over time he will figure out that there are some benefits to being on his stomach, and he will start to stay there longer and longer by his own choosing.
Learning to Roll Over
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