It likely needs FCC certification because the box could accidentally act as an antenna (or the RPi might be subject to different regulations than the product).

There are also safety concerns, temperature and humidity testing, and so on to consider.

Absolutely, yes.

Think of it this way: If current runs through it, you need to cert it. Period.

Edit: I think the Pi might already have FCC so if you are NOT electrically altering the Pi in anyway, then you won't need to re-cert (as you are essentially installing software on it and for a consumer device FCC doesn't have ESD requirements).

For CE, depending on the directive, you'd need to do ESD (adding a box will alter that).

Disclaimer: Not compliance advice.