IINM, picnic roast is the same as shoulder roast.
It has a bone, a ton of meat, and a large slab of “fat” that sort of encases it, mostly on one side.
If that’s what you’re talking about, it’s one of the most succulent, awesome cuts of meat out there. I think it has the perfect meat to fat ratio for keeping it moist, but not too fatty.
What I do is liberally apply salt & pepper, and some herbs to the outside of the meat.
I heat my charcoal grill using the “indirect” method. Coals on the outside. The roast goes in the middle over a drip pan. I’ll have the grill cranked for a while, but then I shut the valves a little, and cook it for 4+ hours until a thermometer gives about 160-180.
I add coals every hour.
Then, I shred the meat using two forks, and voila, pulled pork. It’s moist, flavorful, and a canvas for an enormous array of possibilities at this point.
Pork burritos, with mole sauce and black beans.
Pork sandwiches with a classic sweet/tomato sauce.
Pork sandwiches with a Carolina vinegar/mustard sauce.
Just a pile of pork that you can eat with a tangy cole slaw.
You can probably roast this in an oven. . .start it at 500, and roll it back to maybe 250? There are lots of recipes for this, probably mostly in barbeque books.
I’m not a big fan of smoking, but you can probably do that too. When you shred the meat, the crusty outside parts get mixed with the moist inside parts for a great melding of flavors/textures.
Awesome cut of meat.