nut rolls

It sounds like you spread the filling to close to the edges.

It's a combination of factors. The filling usually has a high proportion of meltable ingredients (fats and sugars) that, when baked, turn the mix into a sort of slurry. That mix has a tendency to glide over the surface of whatever it's on, without being absorbed, because unlike water, doughs won't readily absorb melted sugar or fat.

Then, when you put the item in the oven, the dough immediately begins to expand. Now, the filling doesn't expand (because it doesn't have large quantities of structural ingredients (flours and eggs) that would puff out. So as the expanding dough presses against the melted, slurry-like mix of the filling, it naturally squeezes it, like a toothpaste tube.

If, then, you spread the filling close to the edges, or overfill, the volume that remains as the dough expands isn't big enough to hold the amount of filling you have inside what pockets exist in the dough. That's why it oozes out.

Pricking with a fork in the case of sealed pastries like pies is done for a different reason. In a sealed pastry, as it bakes, the filling inside will at some point reach boiling. As it heats up it generates a lot of steam, and, if there's no fork-holes to release the pressure, it builds up until some part of the pastry (almost always the crimp) blows out. A blowout is nasty because that much of a pressure release would spurt out filling rather like a volcano. Net result is a *very* ugly mess in the oven.

Now, if you have a sealed pastry which has been filled 'till it's packed full, even with prick marks, the expanding dough will press the filling and probably push some out through the forkholes. It's more of a controlled flow, though, so that's preferable to a blowout.

The real point in all this is that generally, for pastries of any reasonable size (i.e. not giant), the amount of filling that you can really put into it without oozing is surprisingly small. Often only 1 or at most 2 tbsp of filling will actually fit. Generally when filling pastries it's wisest to be sparing rather than generous.