Easy Breakfast Casserole

2 1/2 cups seasoned croutons
1 pd sausage roll
4 eggs
2 1/4 cups milk
1 can condensed cream of mushroom soup
10 ounces chopped spinach
4 ounces chopped mushrooms
1 cup shredded cheddar cheese
1 cup shredded monterey jack cheese
1/4 tsp dry mustard
salsa