You can place a glass casserole or other glass baking dish into the freezer but you should wait until the food has fully cooled off including the glass baking dish before placing it in the freezer to prevent cracking or breaking of the glass casserole dish.
Also don't put the glass casserole dish right into a hot oven when you just removed the glass casserole dish from the freezer because the heat thawing it out quickly after being frozen could break the glass casserole dish.
Take the casserole dish out of the freezer and wait until it thaws out and then place the glass casserole dish into the oven and it should not break.