Slow Cooker Beef Roast with Mushrooms & Carrots

-ish lb. beef roast (I purchased a 3.89 # roast and split it into 2 freezer packs!)

Salt and pepper

garlic powder

chopped onion (or 2 Tbsp minced onion)

about 1 cup sliced white mushrooms

about 1 lb. baby carrots or peeled carrot sticks

Side dishes: dinner roll, other optional frozen veggies