Line a 33 cm x 23 cm Pyrex dish with rolls, sealing perforations. Cover with sausage, mushrooms and half the cheese. Mix eggs with soup and pour over casserole. Sprinkle remaining cheese on top. Chill overnight.
Bake at 180ºC or 1 hour.
Note: For variation, you can use cooked, crumbled bacon or bite-sized pieces of ham instead of sausage.