I love a good pot roast. I do admit, that one of the best pot roasts I have made was in the crock pot.
http://www.food.com/recipe/pot-roast-in-a-crock-pot-11699
This is a good starting point.
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To this I added worcestershire, bay leaves, more dry seasoning; and then fresh parsley to finish it off.
I also seasoned my meat with s/p, paprika, garlic powder, and onion powder first, then pan seared in olive oil before adding to the crock pot.
Also, to the pot my vegetables, were baby red potatoes, carrots, celery, onions, parsnips, and mushrooms. I finished with peas right at the end.
All the vegetables were cut in similar size pieces, about 1" size pieces. NOT too small for me.
After the roast is done, remove to let rest with the vegetables. Transfer the gravy to a pot, strain, then thicken with a little slurry of corn starch and water.
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Edit: I add mushrooms for me; and, peas for my Dad. Both are not the norm, but I really enjoy whole mushrooms. And for some reason, the peas just look cool. But obviously, use the veggies you like best. My friend uses turnips.