I go ahead and cook both roasts (using an envelope of onion soup mix and a can of mushroom soup...baking at 275 for about 3 1/2 - 4 hours). We eat what we want for dinner, then I cut the leftover meat into bite-sized pieces, separating into several meal-sized portions and put in zip-lock freezer bags. I pour any gravy over the top of the meat and freeze. This usually makes at least three bags for three more meals.
When I'm ready to use one of the bags, I just put it in the crockpot frozen, add some baby carrots and peeled, chunked potatoes, and another can of cream of mushroom soup. I usually sprinkle some brown gravy mix over the top, then let it cook on low for about 6 hours - or until the veggies are done. Serve over rice.
For more make ahead meal ideas, head over to the recipe swap at the Life as Mom blog.