When I first saw those it was wtf??? Some thoughtful insight and planning ahead had to go into the initial design of that trailer. Most now are just generic with add-ons. Probably the reason the boat bottom is arrow straight.
Couple things I'd like to add.
If when you remove the rollers you will see one end of the pin has a square end and the othe end is cut at about a forty five. Figure out which side is which. Most of the time the drivers side of a car is the angled end. That is the end you want to push back. Then drive the pin down or it may just fall into the tongue. Now the original pins are metal so a magnet is an easy way to retrieve them. Try not to bend back both side tabs if you do not have to. These tabs have a bit of a C bend to them from the factory and when you drive them back you will tend to straighten them ( take out the C bend) . Yes before you reinstall you take a screw driver and bend them back but the tabs tend to want to straighten out. This makes it hard to get the pin it stay in the tab when you reinsert them.
One other thing make sure you put your rollers back before you paint. It is almost impossible to reinstall and not wreck you paint.