Re_keying Rotalok

I don't know that product, but with most rekeyable padlocks you start by unlocking the shackle, then if you look into the bottom of the shackle hole you'll see a fastener of some type; unscrewing that releases the retainer and allows the cylinder to be removed for rekeying or replacement.

The main exception is locks based on Interchangable Cores, where you need a control key (which is _not_ the key normally used to operate the lock) to remove the cylinder.

There are a few other variants, all designed to keep the disassembly process from compromising the lock's security.

If you really need to know, write to the manufacturer and ask; they may be willing to send you the instruction sheet.