preheat oven to 350
Cook the shells according to the packet directions, strain and let them cool.
Mix cheeses, rosemary, salt and pepper
fill the shells with a spoon.
Pour a little sauce in bottom of 9x9 pan, put the shells in, pour rest of sauce on, sprinkle extra cheese on top.
Cook 20-40 min at 350. It's simply to warm it completely.
I just watch the sauce, and when it starts to bubble it's done.