Obviously there are major differences if the pot roast is cooked uncovered in the oven. That aside, are there differences if it is covered? 
Tubes like that are assembled with the bottom open (so at that point it's a cylinder, closed at the cap end), filled, and then folded and heat-sealed at the bottom. The filling is done with a rigid baster-like thing to minimize air bubbles. Here's a video of the process. There's no particular reason you couldn't do most of this at home, with the exception of the heat sealer (though you might be able to repurpose a vacuum sealer). The real issue would be sourcing the tubes, which I doubt are generally available if you're buying less than a thousand. If your primary goal is easy dispensability, have you considered a large food-safe syringe? Easy to find, similar in functionality, and while they're more expensive than foil tubes they're also reusable. 