Can I give my rats stuff from the butchers. like marrowbone, pigs ears etc.?
Obviously, without added salt, flavourings etc.
What about meal worms or live foods?
You absolutely can. They're tasty and great for keeping their teeth trimmed. Pig's ears are very, very fatty for them though, so bear that in mind. Meal worms are great too, as a tasty source of protein, alive or dried. They can also have other live foods such as crickets etc, though I prefer to only feed these dried as rats tend to stash food and you may discover a bunch of mealworms living in your cage. It can get messy. I'd recommend only feeding live in small doses and at times when you can make sure the rats aren't stashing!
Bones are a particular favourite of mine, I gave them a chicken carcass today actually.