Should I cook the pot roast on high or low

Traditionally roasting used radiant heat to cook meat. This would have taken place over an open flame, typically on a rotating spit. In modern times this method is now called Rotisserie. Modern roasting refers to dry heat cooking that takes place in an oven, the food is cooked by convection. Until the late 19th century this method was referred to as baking.

Baking is essentially the same as roasting in modern times. Baking most often refers specifically to the cooking of "baked goods" (breads, pastries, etc.). However, the terms baking and roasting are often used interchangeably (baked chicken, roast chicken). There doesn't seem to be a hard and fast rule here as to which term is used. For example, you roast asparagus, turkey, chicken, but bake lasagna, casseroles, and also chicken.

Braising uses a combination of moist and dry heat to cook the food. This is what occurs in a crock pot, or in dutch oven/stock pot in the oven. Your meat will be cooked in an ample amount of seasoned liquid such as wine and/or stock.

Broasting I had never heard of before. According to Wikipedia it's a trademarked method of pressurized deep frying. I doubt this is what you were referring to.

It depends on what kind of settings your crock pot has. A low simmer on the stove is probably equivalent to something fairly low on your slow cooker, though. If all you have is warm, low, and high, you want low - in some cases it might be too hot, though. You're aiming for just short of boiling, so a setting that gets you a few bubbles now and then is good. More than that and you're cooking a bit vigorously, and on a "warm" setting you likely aren't heating it enough to cook properly and stay safe. If you have some kind of continuous settings, you can possibly adjust to get exactly where you want!