I do not recommend boiling an entire roast, the taste will be very bland, and the outside will become too dry. Here is one of my favorite recipes that I found online:

1 pork butt roast (weighs about 4 pounds)
1/4 to 1/3 cup of Worcestershire sauce (optional)
3/4 cup of light brown sugar
1 cup of apple juice
1/2 teaspoon of salt

1. Preheat the oven to 400 F.
2. Prepare the roast by cleaning and trimming some fat.
3. Place the pork roast in a casserole dish with a lid.
4. Cover the pork roast with Worcestershire sauce (if adding).
5. Pat brown sugar on to the roast, covering everywhere.
6. Add apple juice to the bottom of the casserole dish, being careful not to get the roast.
7. Place the roast in the oven with a lid. Turn the temperature down to 200 F, and bake for 5 hours.
8. When the roast is done, it should be falling off the bone. If it is not ready, bake for 30 more minutes, or cook until done.

I don't think it would work all that well to boil it, It would end up a bit like ham, but with less taste.

The best roast pork is fairly simple, Have a look at Delia Smiths method which is pretty much what I do, but I don't always use the cider, it stays moist and has delicious crispy crackling.

"Preparation time, 30 mins

Cooking time: over 2 hours

Serves 8
Roast pork with crackling

A pork joint coated in crunchy crackling is always welcome at the table, but when it’s Delia Smith’s perfect roast pork, it’s the guest of honour.
Ingredients

*

2.25kg/5lb loin of pork, bottom bone removed, top bone left in
*

1 small, onion peeled
*

1 tbsp plain flour
*

275ml/10fl oz dry cider
*

275ml/10fl oz vegetable stock (or potato water)
*

sea salt and freshly milled black pepper

Preparation method

1.

Pre-heat the oven to 240C/475F/Gas 9.
2.

While the oven is preheating, score the skin of the pork. It will be scored already, but it's always best to add a few more lines. To do this you can use the point of a very sharp paring knife, or Stanley knife, or you can now even buy a special scalpel from a good quality kitchen shop! What you need to do is score the skin all over into thin strips, bringing the blade of the knife about halfway through the fat beneath the skin.

3.

Now place the pork in a tin, skin-side up, halve the onion and wedge the two pieces in slightly underneath the meat. Now take about 1 tbsp of crushed salt crystals and sprinkle it evenly over the skin, pressing it in as much as you can.
4.

Place the pork on a high shelf in the oven and roast it for 25 minutes. Turn the heat down to 190C/375F/Gas 5, and calculate the total cooking time allowing 35 minutes to the pound. In this case it would be a further 2½ hours.
5.

There's no need to baste pork as there is enough fat to keep the meat moist. The way to tell if the meat is cooked is to insert a skewer in the thickest part and the juices that run out should be absolutely clear without any trace of pinkness.
6.

When the pork is cooked remove it from the oven and give it at least 30 minutes resting time before carving. While that is happening, tilt the tin and spoon all the fat off, leaving only the juices. The onion will probably be black and charred, which gives the gravy a lovely rich colour. Leave the onion in, then place the roasting tin over direct heat, turned to low, sprinkle in the flour and quickly work it into the juices with a wooden spoon.
7.

Now turn the heat up to medium and gradually add the cider and the stock, this time using a balloon whisk until it comes up to simmering point and you have a smooth rich gravy. Taste and season with salt and pepper, then discard the onion and pour the gravy into a warmed serving jug. Serve the pork carved in slices, giving everyone some crackling."

I find when i make a pork roast just a small one for me and my gf that I put my roast in a baking pan add potatoes and whatever ad a cup or two of water with seasoning I bake it on 350 for 45 mins then i put it up to 400 for 20 or thirty mins. its nice and juicy. That just with a small roast. But before i put it an the oven i braze it ins a skillet to make all sides brown first then bake it that helps to hold the juices in. Temp and time varies differently due to the size of the roast.