I am about to put a roast beef in the crock pot.?

The recipe says to cook on low for 7 hrs. My concern is that there is hardly any liquid involved in this recipe. About 2 tablespoons. Is that going to be enough liquid? Is there any rule of thumb as far as how much liquid should be used?

Yes! That's enough, you don't want to add liquid it will become soup. It makes it's own liquid! I made that mistake before. Tip, brown the meat in skillet, remove, add Tablespoon of flour in drippings, then pour in a can of cream of mushroom(no water), put meat back in to coat. Place a layer of onion on the bottom, then the roast, pour remaining skillet mix on top and top with more onions Don't add water!!!!!!!.