I don't really like any of the pot roast seasoning packets, and whenever I pick and choose seasonings in my cabinets bad things happen, so I've always bought a package of onion soup or dip mix. It's really good and adds nice flavor to the roast.
Add your meat first with the fat up then dump all the season on it. I added about 1/4 cup of water for extra juice because pork isn't as juicy as beef is. Next add whatever chopped up veggies you would like. I added two potatoes, one onion, and about four carrots (mostly for color because I hate soggy carrots).
The fun part about a crock pot is you can just leave it cooking and it will just keep simmering and simmering. Now, if you let it simmer too long you'll have mush for dinner, but at least it won't burn.
Depending on how many pounds your roast is, I'd cook it on high for 4-5 hours or on low for 8. As long as it doesn't dry out though, you should be fine to keep cooking it.
I check if it's done the same way I check fish: I stick a fork in it and turn the fork to see if them meat falls apart easily. I could also see that the pork was very white inside so I knew it was good. You can tell how white and mushy all the veggies were, too. Before serving I used a ladle and poured juice up on the veggies.
You can see what I mean about a "white dinner" but it tastes fantastic and was really easy to make because my crock pot did all the work for me! I even took a nap and woke up to the yummy smells of dinner. How often does a woman get to do that?