It's unsafe because unlike other vaccines rotavirus is completely useless in modern countries.

The point which you are overlooking is that even something as tested as vaccines still had an undiscovered problem. So you are being overconfident.

You want to say the risk is low enough that it's worth it? Fine. But do not be so quick to dismiss concerns.

PS your math for 40 cases a year seems incorrect, there are considerably more than half a million babies born each year.