[Renlikescake]

Hamsters can only be litter trained to pee in the tray. They will still poo around their cage as they have a very fast metabolism they can't really control it. I've litter trained nearly all of my hamsters but they would still poo in places they spend slit of time in such as their wheel and their nest.
Once she pees in her tray she's pretty much trained. I also highly recommend using sand and not potty litter, it's much better for them.
They will roll in it-completely normal.
Also I personally find that makes take longer to train than females but that may just be me.
Good luck in your training