We find we use Roaster Ovens far more than a crock pot. The crock pot is usually very limited in cooking volume with most falling under 5 quarts.
Here we live in an arid, hot, dry, climate in the summer. So you want to cook as little as possible inside. It just heats up the whole place.
I've two different size Roaster Ovens, one 12 quart and one 16 quart. So enough is cooked at one time for many meals. What is done is to take out how much you will eat and then bag and freeze the rest in meal sized servings. When you want it again all you have to do is defrost and then microwave to warm. No additional heat in the place to deal with.
The other difference between a crock pot and a roaster oven is the crock pot usually has two settings for heat, high and low. The roaster oven has an adjustable heat setting. You can go from low heat, long cook time to upwards of 400 F, giving you a wide range of cooking, including steaming.