Eye of Round will work nicely in your crock-pot. I would cut slits in it and add bacon lardoons to add favor. Also, smother the roast in onion-slices and add enough water to come half-way up on the roast. Lightly salt, put the top on, cook on low all day. For extra flavor, heat a small amount (about 2 tbs.) cooking oil in a heavy (I love my cast-iron) pan and sear the roast on all sides until browned. Then put in the crock-pot.
To turn this into a pot roast, add carrots and potatoes, and maybe some green beans to the pot.
An alternate way of cooking this meal is to do it in a aroasting pan with little water, and a slow oven (220 degrees F.) for 4 to 5 hours. Then you can use the jucies and fat to make Yorkshire Pudding.