A barrell roll isn't that big of a deal. Well, maybe more of an ailerion roll. Barrel rolls are a tad more advanced but even those don't put much stress on the bird. Was told by a Navy pilot once that they were taught to roll a T-34 in such a way that a glass of water on top of the instrument panel would not spill a drop. It is a pretty mild manuver, just somewhat disconcerting if you haven't done it before. Nose down, pick up speed to x, pull the nose up to about 15 degrees above the horizon and push the stick over to the side of your leg, holding it there until you come right side up (jockeying the rudders) then neutralize the controls and you should be slightly nose down.
Loop is a little more involved. Nose down, to speed of x (x is whatever you need to do the full manuver- oh and full power on both manuvers), stick back in your stomach (don't let up going over the top when you start floating a bit), go over the top and throttle back a bit coming down the back side or you'll really be moving at the bottom. The problem is the stress really builds up at the bottom of the loop. At least it can. Also, you could get negative g going over the top if you lose it a bit.
I think you can roll a Lanc relatively easily. Loop it? Not if you didn't have to. I read that story in the book mentioned by Geedee and think that crew was very, very lucky. Others probably did it and didn't live to tell about it.