Jean, can you figure out if I found the correct Misroslav or not? If I did, this index, etc. is fairly complete. If the family was not Catholic, there might be books for the Evangelical Brethren, but usually they show up on the list, even if they are not digitized. I looked at a few pages in this book to see if protestant was ever checked, but did not see any. (I have seen books where protestant was checked, and even a Jewish entry.)
If this is the correct book, and if protestants are listed, then those two children were not born in Miroslav. That's why I was hoping that the entry I found was possibly another Rosst family, but it was not to be. By following back relatives, you sometimes get a clue where the missing ones are.