You can do the same thing in the crockpot. Just rub your roast down with a bit of salt,
pepper, garlic powder, and maybe a teeny bit of cayenne
pepper if you like a little spice, and stick it in the crockpot in the morning. I add a bit of water too, just because I'm paranoid about burning stuff up (after what I did to a chicken in the crockpot shortly after we got married), and cook it on low until shortly before supper.
Then do the same thing Catherine said, and it will come out really good.
The main thing is, don't start out with a fancy cut of meat.
Happy Barbecue!