I prefer to use the oven for pot roasts because I like them better than in a crock pot. But if you have to use a crockpot because of work, don't cover roast with water. Just put in enough to cover bottom of crock pot.
I use chuck roasts. They are cheaper and in my opinion, better tasting than the expensive cuts.
1 roast
1 can cream of mushroom soup
1 can of Coca Cola (Coke brand is best)
1 package of Lipton onion soup mix
Potatoes and carrots to put around roast
Put roast in pan. Place carrots and potatoes around roast. Put in just enough water to cover bottom of pan. Then spoon cream of mushroom soup over top of meat and veggies. Sprinkle onion soup mix over top of this. Then, pour can of Coke over top of all. Cover with aluminum foil and bake in preheated 350 oven for 2 1/2 to 3 hours.
If using the crockpot, the only difference is put on low all day.