Emmy Rossum Robbed of Jewelry

Emmy Rossum's West L.A. home was hit by burglars who targeted 2 safes, and she made it easy for them to pull off the heist ... because she left the combos right there.

Law enforcement sources tell us, Emmy was in NYC last week when the housekeeper showed up on Wednesday and everything was fine. But on Friday, the housekeeper returned to a crime scene.

The housekeeper noticed the power was off and a glass pane on a back door was smashed.

The next thing the housekeeper saw ... the "Shameless" star's 2 safes were wide open with nothing inside.

Our sources say $150,000 in antique jewelry was missing from the safes ... nothing else was taken.

As for how the burglars were able to open them ... we're told Emmy left written combinations next to the safes.

Law enforcement believes the thieves cut the power to deactivate the alarm system.