The Picnic Roast is the lower half of the shoulder, the top half being called the Boston Butt. This cut can be combined into both and the cooking options are similar. This is a heavily used muscle and a flavorful meat with good fat and connective tissue that will render when cooked low and slow.
Over at the Dizzy Pig site, they have a recipe for pulled pork that uses both of these shoulder cuts to make pulled pork, an all time favorite. The low and slow method is at the extreme here, but the results are worth it. Check it out for it’s nice explanation and detailed instructions and options.
Ultra-Crispy Slow-Roasted Pork Shoulder is a favorite of mine, due in large part to the delicious cracklin from the final step in the process that produces crackles on the outer layer. The recipe at serious eats has some nice suggestions on this that you can build on with links to sauces and related dishes. Additionally, this is a simple meal to make though you will have to plan ahead and budget 8-10 hrs.
The general rule to keep in mind for shoulder cuts is that you need to cook it at low temp for a long time to melt all the fat and connective tissue, but they are rich and flavorful cuts. If you have smaller roast, you will reduce the cooking / smoking time accordingly.
I encourage you to check out AmazingRibs for a very good article on cooking temps and times. This is a great site overall to familiarize yourself with and you will find we link to it frequently.