There are a few rules. JDP asked the right question. What kind of roast are you smoking, as various types will require slightly different methods.
One thing is certain, no matter which method you use. You must know the meat temperature to determine when the pork is done.
A fresh ham is very lean and can easily dry out if not smoked properly. And if using the fresh ham, are you trying to come up with a smoked roast, or a smoked ham. For a simple smoked fresh ham, brine it, then place in your smoker, keeping the temperature low, no more than 180 ' or so. It will take a long time to cook at that temperature, but that will give the smoke a chance to flavor the entire piece of meat. Remove the meat when the internal temperature reaches 155 degrees in the thickest part of the roast.
If you are trying to achieve a pork roast, with a smokey flavor, use a higher temperature and a covered grill rather than your smoker. You might also want to cut small slits into the roast and fill with bacon or pork-fat lardoons to help keep the fresh ham moist. You can also brush this meat with a honey/mustard glaze, or your favorite barbecue sauce. Use indirect heat and use the smoking wood to block the radiant heat from reaching the food. Again, remove the roast when a temp. of 155 is attained.
For a pork butt, there is no need to use lardoons as this cut has more natural fat in it. Smoking and barbecuing directions are the same as for the ham, but as the butt is smaller, it won't take as much time to cook. And you can brine or not as you prefer and still come out with a great chunk of meat.
For a truly smoked meat, you will need to look for a "smoke ring". That is, the smoke will create a discoloration of the meat (it will be somewhat pinkish as the smoke acts as a coloring agent, like with hot dogs, only in hot dogs, that pink color is the result of salt peter).
Again, use indirect heat too cook the roast.
The key to flavorful, tender, and juicy meat is to keep the internal temperature below 170 degrees F., IMHO, and based on years of experience and careful study of meat properties.
My sugestion, try using the smoker with both a ham, and a pork butt, brining the ham and using a glaze on the butt. Then try cooking both on a covered grill, using the wood to provide smoke. Taste and see which you like better.
Myself, I prefer a good pork butt, seasoned lightly with salt, pepper, and a bit of sage, thrown into a 465 degree oven with a meat thermometer, and removed when the temp reaches 150. But I adore pork chops cooked on the grill, with apple wood providing the smoke. But that's just me. Oh, and that same pork butt makes phonominal pulled pork as well.
So try out a few techniques and develop your own opinions. After all, food likes and dislikes are a complicated thing, having to do with what you are used to, fond memory associations, how well your sniffer works, and your particular tastes, not to mention the sensitivity of your tastebuds.
You will learn what you prefer, along with the preferences of your family.
Hope that helps.
Seeeeeeya; Goodweed of the North