Chances are your going to find those rocks being spit up over the next couple of days... or weeks.... or months... it's suprising how much they will eat and how long it can take for them to "expell" them. Depending on the size of the rocks I wouldn't be to worried about them coming out the other end... unless they are fairly small in which case I would be VERY CONCERNED if they come out the other end they could do some serious damage along the way.
So the ultimate question right now is... What size of rocks are they?