Try to thaw them out in warm / hot water and present the pinkys while they're still warm. It's also helpful to offer them on forceps so that the pinky looks like its moving. If it goes for it, tug on the pinky's tail while the snake is constricting (sometimes they'll let go and lose interest if the pinky doesn't "struggle". Let it go a couple of weeks without food before you try with a thawed. Not all rosys are willing to convert; good luck and I hope the preceding works for you.

-Alice