Hi, and welcome to the club! Great to have you with us! Now that you're here, it would great if you'd head over to the Introductions section and tell us about yourself (like BBQ experience), so we know your experience level. It's also great to add a first name, and town, to your signature line, so we know you better. We're pretty informal and familiar, around here!
To answer your question -
yes and
no. I need more information... what kind of pork roasts are you using? 3 lbs is really small, and will not smoke well. Small cuts (under about 7 lbs), that require a "stall" (where the internal fat renders for several hours, and the temperature stops climbing) are unpredictable. This happens more with briskets, but pork roasts can too. Now, if you are smoking, say, two 7 lb Boston butts, they will time like one, not a 14 lb hunk of meat.
Since you just said "pork roast," I'll give you my nickels-worth of 2¢...
There are several types of cuts that stores just label "pork roast," but they are
far from the same! I've seen 2 or 3 lb sections of pork loin labeled "pork roast." This would be a terrible cut for pulled pork; way too lean! What's common, in some regions, is to label a "picnic roast" as a pork roast. You can tell the picnic cut because it has a straight bone and is usually cone-shaped (like a ham). The picnic is the lower portion of the front leg. This is a good cut for curing like ham, or for slicing, but not preferred for pulled pork.
Now for "the money" advice (the extra 3¢-worth): Get a bone-in Boston butt pork shoulder, 7+ lbs, if you want the best pulled pork! The Boston butt is the upper shoulder of the hog. It has a blade-shaped bone, and is the absolute preference of all serious smokers (even competition). If you need to know the best way I know to prepare one, check out this post:
Brined Boston Butt for Pulled Pork
Stay away from the little 3 lb unidentified cuts, and go with what works! Your dinner guests will sing your praises as the best Pit Master they've ever known!
